NL-78-66

PHYSICS DIVISION

ANNUAL REVIEW

1 April 1977-31

ANL--78-66

MASTER

March 1978

K!

'4 m

ASof C -AUA -USOOE

ARGONNE NATIONAL LABORATORY, ARGONNE, ILLINOIS

Prepared for the U. S. DEPARTMENT OF ENERGYunder Contract W-31-109-Eng-38

Ph11 'iCs -- GetTl nr' (UJC-34)

A:\N .- 7S-66(

A ( G)TKN 1 . I A BC)IK IA TO Y

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J I iin)IS (>O.139

PHYSICS DIVISION ANNU+. PEVIEIW1 APT IL ?-97/ -31 WfARCH 1>

Annr R evi c%I 75 -- 1 67N 7 -7

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9700 So-\r no

n3 o Annuir ! l (-,"iew

A !- -7 5, MAAn u . 1R Uri Y- 1 ?7----1 79

ii

FOR WORD

The Physics Division Annual Reviewk'

presents a ruroad but necessarily incomplte view of

th- r-sea rch activity within the Division for th- ya;r

r-nding in :\uril 1978.

At the back of this report a complt-te

list of publications along with the Divisional roster

c'an be found.

ii

TABLE OF CONTENTS

NUCLEAR PHYSICS RESEARCH I

INTRODUCTION 1

I. THE SUPERCONDUCT ING L INAC

INTRODU)TIC TON

A. II AVY-ION ENERGY BOOST-' f,

1 . AIN F AT II ;I ES OF TI V DESIGN F>

2. T A IV TS 01F TIII. R OJIT'T 11

. Proto p v)& t'sOfnatorS I I

b)._ 1'r F i (Ii n-\1V od I Iigh - Ig ta R( sonaturs 1 2

< : F C ont rte 13

d. h.in-t Control S\-stvm 13

. ('rvostats 13

f. Ileliun Refri r,'itn 11

g. lirn n Systern 1-I

3. PLANS FOR TIE NEAR FUTURE 14

B. INV ESTIGA TIONS OF SUP ER CONDUCTING- I.IN:\C lt6T1 TECHNOLOGY

1. MATERIA LS AND FABRICATION TECHNIQU ES 1o

2. R ESONATOR DIAGNOSTIC TECINIQUIES 17

3. RF-PHASE CONTROL 17

4. BEAM-DYNAMICS CO'lPUTER PROGR AMS 18

5. ASYMMETRY IN ACCELERATING FIELD 19

6. SURFACE-TREATMENT TECHNIQUES 19

C. PROPOSAL FOR ATLAS 20

iv

Page

II. MEDIUM-ENERGY PHYSICS

INT R ODUC I ION

a. Ganmrna -Ray Study l)f lion -Induced Reactions on

C olmplex Nuclei

b. Sturly of Pion Absorption Mechanisms in 4He and

Other Nuclei

C Prop < rti es of Inc lusive (Tr wO) Ractiolns in

Nuclei

d. Double -Charge-Ixclange Pion Peacti ons

e. S( ;ttte ring of Pions by Complex Nuclei

f. Low- Energ. Pion Elastic Scattering from the

Proton and Deuteron at 180c'

g. The Channeling of Tr Msc oils

III. HEAVY-ION PHYSICS

INT RODUC;TION

1. FUSION CBOSS SECTIONS

a. Maximum Fusion :.-oss Section for

b. I easuremrient of tlh

Sections

C + 15N12 13

C + C Fusion Cross

c. Structure in the Fusion of 160+ 160

d. Measurement of Fusion Cross Sections for16, 180 + 24, 2 6 Mg Reactions

e. Energy Dependence of Total Fusion Cros :

Section for (12C + 2 4 Mg)

f. Nucleus -Nucleus ?otential for the C) 40 Ca

Sy stem

2. SHELL EFFECTS AND RESONANCES IN ELASTICSCATTERING

a. Elastic Scattering of 12C from Ca Isotopes

b. 40Ca + 12C Back-Angle Elastic-Excitation

Function

c. Resonant Effects in the 24Mg(16 12C)28 iReaction

23

23

24

26

27

28

29

31

32

35

35

36

37

37

38

40

41

42

43

43

43

44

v

Page

3. STUDY OF QUASIELASTIC DIR ECT IPROCESSVS 46

a. Inelastic S uttering of i60 on Even -(a Isotop 1 s -46

b. Energy Dependence of Quasielastic Processes 48

in 160 + 4 0 , 4 8 Ca R actions

1 0C. '.ec hansim of Direct R ea tions Induced by 0 49on (a

16 12 18 14d. TI ( 0, C;) and (1 ), (4C) Reactions ;InId the 50

Quasielastic Cross Section As a '-ne tion ofMass Number

4. HEAVY -ION -INDU E:ID FISSION ANI) QCt\SIIJSSION 519

a. IIe avy -Ion -Induced Fission at Iii h Angul. r 0

MTomnicta

b. Quasifission Pt-actions Indu( ed b 23k1 -MeV Ar 51

L2 L i, ffr,JFLindi Xi 'I rget s

C. Fission Char. etc risti s of tie ( <m site Sys te ccm 51323 0r

5. IIIGI ANGU LAR MOMENTUM STAT ES IN NUCLEI 52

a. Search for Iligh Spin Isomers 53

b. High-Spin Structure of 147Gd and Dcvelopment 53of an Energy.-Sum Spectromete r

r. Study of Iigh Spin Isomeric States Near the 54Closed Neutron Shcll, N= 82

16d. Pd( Oxn)Me

e. Heavy-Ion Coulomb Excitation in =,148, 150, 1 5 2 , 1 5 4 Sm

f. Heavy-Ion Composite X Rays b0

6. NEW BEAM LINE FOR THE SUPERCONDUCTING 60LINAC BOOSTER

a. Zero Degree Beam Line for New Experimental 61

Area

b. Target Station for Delayed Activities on the 62

Superconducting Linac

c. Beam Optics for the Zero Degree Beam Line 62

d. Beam Diagnostics in the New Target Area 63

vi

Page

e. VTuumn Systen in New Target Area 63

f. 65-in. Scattering Chamber in New fTarget Area 64

g.mi-av Facilit for the New 0O Beam Line 64

7. EQUIPMENT DEVELOPMENT 65

I Hleavv-Ion Focal Plane Detectors for the 65

Magnetic Spectrograph

b. Nuclear Target Making and D(velopm nt 66

IV. CHARGED-PARTICLE RESEARCH 69

INTRODUCTION 69

A. CHARGED-PARTfIC1 E REISEAR CIH AT TIII DYNAN1TRON 70

6 7 6 7 6a. Li(dp) Li,_Li(d,n) Be, and Li(dl a)n Nuclear 70

Reactions at Low Energies

b. Cross Sections for Three-Body P1reakup in 72

d + hLi Reactions at Low Energy

c. Cross Sections for Light-Ion-Induced >actions 74

on 6 Li at Low Energies

d. Polarization of Neutrons in Isospin-Forbidden 75

(p, n) Reactions

e. Radiative Capture in a(a,Y) Be Through the 76

16.62- and 16.92-MeV Resonances

f. Li(p , a) and 8B((3, a)a Angular Correlations 78

g. Pa rity Violation in the 5. 1 -MeV Doublet of 10B 79

h. Radiative Capture of Alphas on Deuterium 80

i. Search for Light Pseudoscalar Bosons (Axions) 81

in Nuclear Tra.n- itions

j. Search for Fractional +1/3e Charges in Nb, W, 82and Fe Metals

B. CHARGED-PARTICLE RESEARCH AT THE TANDEM 83ACCELERATOR

a. Single-Particle States in Actinide Nu lei 83

b. Comparison Between the Decay Properties of 84

the Isomeric 19/2- State in the Mirror Nuclei4 3 Sc and 4 3 Ti

Positive -Pa rite States in43

i

1. Investigation (f thi V Nucleus

*._3Facturs of N(clear Ltvcls

f. tudic s of Nuclei Fa r fruit Stahilitv

<. An Investigation of the Ground-State Yield of1 8 0 T a P roduc (d by the T I jf(p, n) I 8O0 a R, a cti(l

h. Search for Neutral Cirr lnts in '\1a ss 20

i. NaI Sp( ctronm ttrs

V. ACCELERATOR OPERATIONS

IN'1RODUCT ION

A. TAN I)IENI - LINAC A( c LARATOR

1. OPERATING EXIP 1I 1I :NCE V 1 I II. . ANDENI

2. OIPERAING PLANS FOR I1 i-I INAC

3. UPGRADING OF THE TANDI-.l

a. 'landem-Injection System

b. Iligh-IEnergy and Low-Incrgy Beam ines

C. Tandem Triminal and Tcrrnminal Vontrol

4. 01 I.I DVVELOPIN1ETAL AC I'IVI I I-S7

a. Beam-Bunching System

h. Foil Stripping

5. UNIVERSITY USE. OF THE TANDVNM ACC7ELERATOR

B. DYNAMITRON OPERATiONS

1. OPERATIONAL EXPERIENCE

2. UNIVERSITY USE OF THE DYNAMI1'RON

VI. NEUTRON PHYSICS

INTRODUCTION

A. THR ESHOLD PHOTONEU TRON STUDIES

a. Photodisintegration of the Deuteron

vii

8o

87

88

93

94

94

97

97

101

1 01

102

102

102

1 03

104

1 07

107

t 10

113

113

1 14

115

viii

Page

b. Ground-State Photoneutron Angular Distributions 116for Exciations Between 6. 3 and 9. 3 M(V in 3C:

c. I fects of Radia tive channell and Pot entia l_Capture 1 16

in the R70(, )1 ) action

d. 1)oorway States in jSi( n) 118

e. Search for the Giant Mra gnetic )i ce_ Resonance 119

in 11 9 5n

[. he C ollective XII R esonnc in 208b 2

. CalCUlactiOnf of Differenti<il Pola riziition 121Coefficients for (y, ';rti' le) R actions

12 6h. Studies of the C + n and Li + n Svst ems Below 121

4 1VV

B. M 1IASUR FM lINT O 11-1 E ELECTRIC D)IPOLI MOMENT F 123OF -1 NEUTRON

C. NUC LEAR STRU CTUR E STU DI -S WI 1Il NEUITRONS 125

. NucI a r Structur ( of the Odd-_N Sm Isotopes, 12514 5 Sm, 1 4 9 5r 1 5 15m 1 5 3 Sm cInd 15 5 Sm

14 1 ) 152b. Nucl ;ri Structure_ of Sr, -Im, Sm, 126

and )

. N-utrun (apturv in Iligh Spin Isomeric Stattcs in 123

'1 e Nuc lei

VII. THEORETICAL PHYSICS 131

INTRODUCTION 131

A. HEAVY -ION P .M'(TION "IlLORY 134

(1. Ptolemviv: A Cornputer Prog ram for II ea v%-Ion 136Di rect R ea cti onsz

b. Energy Dependence of Single-Nucleon Tranlsfer 137R actions Induced by 1)0 Ions on Pb

c. Elastic Scattering of Heavy Ions 138

d. Light-Ion-Induced Direct Reactions 139

e. Coupled Channels for Inelastic Excitation 139

f. Surface Delta Potential for Coupled-Channel 140Problem s

B. NUCLEAR ST1RUCTUR E STU_ D I :S 142

a. Non-norrm l Parity States of th- 11) Shall 112

). Odd-Stat( Interaction within th( 1; Shill 14

. Int eriretation of Largp V2 Diff rnr s in 1 IIsoiopcs with N 35 anld 37

\ 1 ph c T Iransf r r for 1 a nd N 'I a rg 145

. evidence for n Isutenlsor Nucleon-NucleOni 146I it era t IoIn

f. I os il Nixing BtI',kei I = 0 and 1 states in 1-S

the 1p Shell

. Prop rti (s of the f Nuclei 1 97/2

h. 'he or c)f the Nu< l i r Shell l<Iud I1)

(;. NU LIAR "1AT rIp TIIEOR Y 1 2

I. SlutiOr( I -V(r 1( I n I n Na lu I -2Mi a ttr

b. Nodel o G ses 1 54

. Ferna i - Iv p, rnett -( !-( hain .iethuds f r the Ground I ;4State of FrrmIon Mla tt: r

ID. INTVIRMDI:)IATFI ENERGY PIYSI(:S 155

1. R I LA TIVI TI(: PARTIC LI QUANTUM MEC \IANICS 155\ I APP LIC.\IION TO IN Ii . EII DIATL 1 IN RGYI A DR ON-NUJ( L llS I?: ACI-INS

. Determination of tih Ilrniltonitn 'a,,11!1 erS 15t,

5. Fast P roton V. m is sion fri )m th .Abs 'rnti In I . 1P o

a Pion

c. Pion-Nucleus Optical 1 otentia1 1;T

d. Pion-Nucleus Inelastic and Singl ha Are- 1 7

Exchange S< a tte r ing

C. Pion-Nucleus Double -(ha rge - xchange Pea action 158--

f. Study on (p, r ) R ca e tons 1 818

2. T-NESON SCATTERING BY 0 159

F. HIGH-ENERGY HEAVY -ION COLLISIONS AND DENSE 160NUCLEAR MATTER

x

1. DENSE NUC LEAR MAT TKER 160

a. Relativistic Calculation of NuIcedr Mattc r and 160the Nuclea r Surfa c

b. Neutron Stars in a Nonlinear M'1afn F ild Iheory 161

2. C LA SSICA L \IICR OSCOPIC: C ALCU LA 'IONS OF 161

1IG1- ENERGY COLLISIONS OF HEAVY IONS

a. 1ilicroscOpic Descriptions of high-En(rg 161i Iav -Ion Collisions

b. N(onr(lativistic and Relativistic Classical 162Microscopic Calculations of High-Energy Ilavy -Ion Collisions

C. Nonrelativistic Cal(ulations with Moncentum- 163Dependent Iottntials

F. MOLECULAR DISSO(IAT'IION AND CHEMICA IL RIEAC LIONS 165

a. Natural (ot lision Coordinates for Mlolecula r 165

Dissociation

b. Dist ributiol of Selected Fragment Vibrations in 166P'olvatomic -Molecule Dissociations

. Rotational Distribuitirns from Photodissociations 166

d. Franck-Condon Fa< 10rs for Chemical Reactions 167

e. A Physical Pa ratil('eri7ation of Density Matrices 167

f. Electron-Atom C(ollisinalT Excitation 169

g. Excitation '\rplitudes for Electron Irnpact of 170

Hydrogen

h. Atom-Diatomic-\Molecular Rotationally Via s tic 170

and Inelastic Collisions

G. OTHER TIIEOR ETICA L HIYSICS 171

a. Axial Currents in Nuclei 171

b. Energy Dependent ft Value and B(M 1) in Be 171

c. Pola rization in Nuclear Reactions Involving

Photons

d. Nuclear Mass Relations and Equations

e. Isospin Restrictions upon Charge Distributions

in Charmed Particle Decays

172

172

173

EXPERIMENTAL ATOMIC AND MOLECULAR PHYSICS RESEARCH 1s

INTRODUCTION 17=

VIII. EXPERIMENTAL ATOMIC AND MOLECULAR PHYSICS 177

\. DISSOCI:\ TION :\NI) 0 1111T IN TI ER AC TIONS OF 1 77KN E R G , II(' N10!E'lCU1AP IONS IN SO L ID .AND

GASES OUS TA RIG'ITS

;. Dissociation of Fast 11-11l Ions in I' oils ;ld 17i

b. Dissocitin of Other litomuic \I lti olt r luns 1 7'

C. Thorctic l N1odul for IDi snciartion (-f FCist 1 s\1 olucula r lons in liuls

(1. I-r nsmiiission Of on il r Ihrullh Foil 1 1

c. ID Xt ruination f 1ol c ul:r-Iun St rug t r's 1I

1. Bl:\N1-FOII. A 1Sl:\ R(: \ND COLIJSION I)YN \\1I' s 183

OF H1: \'Y IONS

a. Ori(untat ion a nd Alignm on of F i st Ions b hin 183Tilted Foils

h. Or nt;rIion and :\linm nt (if Fast ulns b 1841

Grazing Collisions with Surfa0 -

(l ct rig -IF itld Quraiturin I B ats 1 "I

d. Grazing Incidfn(c Spw t ra and I .if'tim ;

. X'-Pay Sp(rtrOs(-opy

f. Doublv- Excited States of 3 -11lc t run Ions I So

g. Cascade Anal\ si s of Bram -Foil Dcciy - tim t So'I easurements

h. Foil Breakage under lleavy-Ion Bormba rdmient 187

i. Optical Observations of Molecular Dissociation 1 87in Thin Foils

C. INTERACTION OF ENERGETIC PARTICLES WITH 189SOLIDS

Xii

;I Corr ;l tion (f I'olist(r )i;irneter af(nd Skin 190T -- i1 kn, 1c s ;n 1id th M(- cha nism of Blister

b. Dejpth Di st ributi'n (f Iflilurn Piubbles in Nic kel 1 91

SInra c tiC vifer t s o>n Surlac I);i j gsuv to 193Simultaneous Irr;rdi;tion of >;i with 1)+ and1 ?

d. Sn rface St ru( ture After Ili hDoIe Ilelinro Ion 195

Irr;!dadiation of Mat( ria ls

-. Surf. I);mir g( i 1 teri;1s for I arn I)urnps 197

( I' 1 1) UnJl(er D- I r ;,rad ia t ifn

f. S utI rig Yic'ls -f r Mo Jnd(r I) I rradiati on it 1981'n. rgi har tr('risti( r>r N rtr, >i m

inje b r ) 1_l

S point \\N I Ku r (lhittov Inistitut( .xp rirn nts on 198

a(111iti on listerirg

h. Joint PPI II-ANL I xpcr(im(fnta on SaIpl( s 199

Ir r;d,(ia ted in P1IT

I). PIIIOTOIONI1 A TION -II TI , 1, I ' FR ON 1 1K I'A R (1 202

1 . R EKS IKA R (: I USING 'I 1I II ON 1 -M 1,1 IKT l IOTOONI - 203NATION AiPlPA A TIJS

a. Ihotodis Sci tivi V' nizition of Meth; nol 203

b. Fr rgmentatiun of 1j ridine [ours and Hfeat of 204FIrtnation of C: I4+

2. REKSEVARC l U1S iNG Tll ] 'I'1 TR 1K1K -M1KI"TE PI1OT0- 205IONIZATION APPARA IIJS

a. _ Franck-(I ondon Fa tors in the Photoionization 20Eof l-

-2b. C ompa rison of Photon bso rption and Photoioniza - " 206

tion of NH at. Hi gh F solution

C. Photoionization of Argon at Hligh Resolution: 206

Collisional Processes Leading to Formation ofAr +

2-d. Photoionization Mass Spectrometry of Neon 208

Using Synchrotron Radiation

e. Photoionization Studies of Molecular Autoionizing 209

Line Profiles in COS and N 2 0

x1ii

f. Phtuioniziti)n \I ss Spectrom tr f CS ;nd 21(

C N-2'-2

3. PI1JOTOiKLAK.: I ON S1I(- 1,ROSCOPY LIKSIKAR(:J 211

. ' c":k 1'ands int I' c-tc d ~ct ron _ nc r. _ cit~ .d_ 1 1

b I h. I i d 11 It I Vight

1. P'hotoelct ron Sptt t r o>f 1(t r iclorid: s "f 211- l htals in Group I ; -

I. IfICGI-I- V.SOIU 'ION SP IKC '1 1;)OS( OPY OF \1IC 1>SAN1 212

WI II TIN A BI-. IVASI IS AN ) A 1)[O , LQUIKNC:Y1 F:C;IINIQU~ I:S

1. %IOSSLAIRI 1 !IPV(: "RSIAII(i 215

;. Generation of D)elI;tvd f-lt rasoindl ini Low- 215

I (-mperat *:re LjHo

1). Int erc; lation of \X non Fll ori d s into Gra phit 21 F,

Confe r nc on New I)ireitions in Mi ossbauer 217

c. YRay Quantorn_ 1_nta s 218

. I )xp) rim ent s \with N; rrow Pr sonances: 181 Ia 221

(K_.2 krV) -__

f. Application o>f ossbae r p< et roscopy to 223

g. Iodine in Sta rch 224

G. M ONOCIIROMAIIC X- RAY I3IEAM I-R OJI-C T 225

_. Calculations for Multiple-C:rysta 1 Nuclear Bragg 225

Scattering

b. Design and Construction of Ciohc rent X-RayFa cility

c. Symmetric Radiant State in Nuclear BraggSc:attering

d. Coherent Nuclear Scattering of Synchrotron

Radiation

e. Temporal Effects of the Hyperfine Interaction

H. SCANNING SECONDARY-ION MICROPROBE

MICROSCOPIC LOCATION OF TRACER ISOTOPES

226

226

226

227

228

228

PUBLICATIONS FROM 1 APRIL 1977 THROUGH 31 MARCH 1978

STAFF MEMBERS OF THE PHYsICS 19IVI SI O[

xiv

231

259

1

NUCLEAR PHYSICS RESEARCH

INTRODUCTION

T'he primary objective of th( nucI, r physics p rogr;I is to

obtain a comprehensiv- under rstanding (f the rm ost ba sic ph non tna in

nuclei. Rese; rch is ca rritcd out undr the rnediumn-en(rgv, heavy-ion,charged -partIce, neutron, and theoreti;1 subpro grams. Our research is

highly coordinated in that the same s( dentists freqiutnt ly pu rsue a sini

scientific goal und(hr ;i variety if .,ubprog rais; oft( i m 1or than on. n1 jorfacility is rploved. We beli0Ve that this problj mrn -orintut I d a pproa h

enables us to obtain the maximum benefit from the digr t;it its ar.d

exptrtis(e of our sc( ntific staff.

The 'hvsics Division op rt(s tw( rni:jor facilities: the FNtandem accei(rator, which is almost com: pletel , dIdicatedA to nuclear r

resea r('h performed b ANL staff ;tnd univ- rsit% ust' rs; and the 1 -IVDvnamnitron, which is ustd about thirty p(r nt fOr nu< lea r scIunt (.

lxporinental photonuclea r studies are carried out at the ANL, (:hcmistryDivision's electron linac. W- a re also us'rs of LAIMP for medium-energyresearch, and occasionally of oth("r facilities for spe cia l (xp rim(ents . In

the coming yea r, the Division's capa Lbility in h avy-i on res(a rch will beenhanced and expanded with the uirgra ding of the T*anden facility havingbe en accornplishtd and th( in production of the suprc onducting linac (post-

Tand(m booster) a an (xp(rirnental facility.

Highlights and Trends

Efforts of the Argonne Physics Division in medium-energy

research continued to gain momentum in the past year with the success of

major phases of three experiments. The Argonne group has demonsti ated

the feasibility of a technique for the direct observation of Trr spectra, taken

pion inelastic scattering data of unexcelled sensitivity and angular resolution

at the EPICS facility, and has completed studies of channeling of positive

and negative pions.

In heavy-ion research, a strong experimental effort continues

to be focussed on questions regarding the reaction processes .present in

heavy-ion reactions, and their relationship to the detailed nuclear structure

of the interacting nuclei. Particularly interesting have been the precise

measurements establishing that resonance structures are present in the

2

ex ititIt)rt functions of -a% ti< and <r 1;istn< ,t' ring, trIn>.i r, and tot;l

flisionr harnel s fVr 'light" hiiv'-iOn s tims. In thIe f;,l1 (t 1')78, this pro-

g rari wil begin to errIplcIO the new shr)er( ow!: tirig her-avy-o lina< bOost' r.

i < r g-d - r:, rI 1(' rus t a r< h, the rrm aso rir 'ln t of ( rt;ain

iSO>'(' t)rr r;rliatiOn , (inths in ,l have 1 - V(4l:,1O(;,lt 1. I}e results speak

IOr the ( o r ved -t >r curr nen' ( )r c e i. arnd r( quire rio 1:- ; ssi rents. 'rpa rations fOr an e'xperlmn nt t;at },1otiI ixhibi tiE 11,4r t

tl w aik lutl ral ror reri s using Al i pa ri I; rrixiing bO t WF (I, tvwO o'( ,' Ili fit(It-s i!1 t1 a- well ntirid rv'ay. I;I rg( tL1 'sr;y srtru n(t'r. that

shY1 r' tr(-1)-takirL; resolution (2. % fnr- 17-MV'V phOtons) a re neI'

Op'r' n i nII I. his d -v 'Optr 'nt wil gr :Itl.' 'nha1 n e Oe r < ,)p1bIlity for

r iia1 iv < t r - stI.i s .

N, l rn Ires n-Oh 1in the P)h 'si< s I)ivisna at A r-gonnw has

b 1 1 ri ti I d ,iitI st < isiv's tel x 1( Ie p rim nIts ' i< h ta e a d anit;g ,f

hi gh I (1 j , 1 li rg O tw 1h 3<,, p t etr. 1 n''i1 i +I.lni w(t a: I A rng in 1 , pr1

vided (1;1. n t ni O I ' 311 pi'' r unl s ( t( )ipw ; int''r st 10 ti( i.tron phy si ( s , but

a Oso un b si e prOb(l 1m n is oh 1(i t p-hy ' s. X1 h( a s lb xisi, 4 oh !iaInt

magni t i -(Iii1Ol r( 's ( aln < .

11 t}h( p st \ ;Ir, maj I Ir i I tin n-w > : ' S r su ri n- c('s

ha;is b)4(1n (14''Uteei ti (lsignt and fabricati(ot Of :t nt'..' t 1( trOtl-bean trIn-Isp( rt

s\ St('m ;111d ('::l si n I1 1. 1 (f thet nl(e t i.r, n - tm -(1 1,ig 11 ints ti Iin 1t 1 t OI1n ; rt( . .

WhV11 m jor in<it n-east inl lina( pr f(t'rm'Utl' t' (t rrl.Iins a h1 ng t rt g 3;l, ,

Ih(s54 mttrt ]liit(i tiolmn al ir1PInroiVC tn-I? .'ill (ilow lhr rngra m tu< r icent ra re- O11 S ver'a1I p)r< Il) n I S <l iIIrlir(11.It it!1 rSt to thi iniucle;or-

s( (it c mt m ( 1111 m tilit .

'1 'ra r Up( :I t ions anid d v('lop)l ert a &tivlit ; iiIn Iuded a

highly V sill' (ssful upgrading (it the I ;ndei3 1 ):bilitIs in (rnergV , stabiIity,

and pita1 sr -spai '(< ()ll r( in prt pa ra t.i n I,o its b irIng tisted as an inje t U- f(r

the supe reotiducting 1iar. Ih linac (evtlm+tpefnlt learn has designed,

evaluated and rhuscn unique split- ring resonator soctitns ,nd has soIv(d

nunerotis ma trials and control 1p rohlem-n s in prepay ,ttion for the post -

accelera lion of h(a-v ions from ; andem-ri in the a rly fa i. tf 19178.

Nuclear theory continues to b.- a major activity of the Argonne

Physics Division. Our main areas of concentration are the theory of heavy-ion reactions, pion-nucleus interactions, the theory of nuclear matter and

nuclear shell theory. During the past year, new techniques and approxima-

tions have been developed that permit a much more thorough study than has

hitherto been possible of the crucial multichannel aspects of heavy-ion direct

reactions at low energies. Studies by the classical equations -of-motion

method of heavy-ion reactions involving neon and argon nuclei at laboratory

energies frornI 100- to s0)-MtNV nut iei, rav ai that individual Innu(lons can

,(quirt1 Lrge momenta as a result of multil)it cAlisions. A rtlativistih

J);t rti( if thturv vith : ohtnomenulugi< al ILtnliltomian has boetn applied tothe inttrp)rtt;tion of ret( tnt ;)i(n-nit u leus scatterinL1 (ai*;;; SU(rm of the effects

tIhe A re snne ;t:id of pi1n t bsOr)t iun a re now 1r?( i< decd. In t I ni c lea r

1p sh elI (7 A 14), a rmpreh nsive she'll-model stu(d of nun-n

p. ritv states Ias be n t(mpltt(I and a ( toijed tale ulitioni of iswericmass-multipt? tenrgies r.t.e;2s the lr(s11n( t of 1l isuttuisor .om-

pfnint't in the tffit.i"e inter< 'ion. In nut Itt rtnutreV torv , ;i-latiiO S

th;t include three -bKrl'; orrelations within th i'ru(kntr :eth.e -G)ltIstone

frtinwe-\e. rk h t ieIldtd sijgnif-i-nt ir np)r(iv(.1 , reem nltflt with th (impn rival

bir.diLn (-nt rL ;,L saltr i t ion (ltnsilt.

I 5

I. THE SUPERCONDUCTING LINAC

L. M. Bollinger, K. W. Shepard, T. P. Wangler, J. Aron,R. Benaroya,1 B. E. Clifft, A. H. Jaffey," K. W. Johnson,

T. K. Kho,,t '. Markovich, J. M. Nixon, and C. i. Schei belhut$

INT K ODUC TION

'he Superconducting Linac Project has two main components,both of which a re (Ievelopm ental in nature. One is the specific task uf

designing, building, and testing a small superconducting linac to serve

as an energy booster for heavy ions from the present FN tandem -lectro-

static accelerator. The second, more general part, consists of investi-

gations of various a spec ts of superconducting rf technology. Although

most of these investigations are now aimtrd at the immediate needs of the

booster, many of them are of fairly general interest for acceleratortechnology.

Both pa rts of the Superconducting Linac Project are jointlysupported and administered by the Chemistry and Physics Divisions.

Chemist rv Division, ANL.

tA ccele rator kesea rcL iPacilities Division, ANL.

l:nfrin,-e(ring Division, ANL.

I

6

A. E11AVY-ION ENERGY BOOSTER

The booster project, stai ted in mid-1975, is considered to

be an essential step in our continuing effort to develop the technology of rf

super, onductivity to the point where it can be used routinely for particle

acceleration. At the s;,me time, the project is aimed at the formation of auseful heavy-ion accelerator system that can srv( as a prototype for

upgrading othe r tandems.

The first year of the project was devoted to the completion of

the cone ptual design of the superconducting linac and to the development of

r;jor components such as resonators. The second year was devoted to

the completion of component development and linac design and to the initia-

tion of component fabrication. During the third y!ear, which ends in

July 1976, cc mIponents are being delivered and installed, and operational

tests of the k:nac are beginning.

1. MAIN FEATURES OF THE DESIGN

A schematic representation of the booster as it is expected

to be in 1980 is shown in Fig. 1. 'he hen rt of the system is the split-

ring resonator, a three-gap structure r ;nade of superconducting niobium.

Supercondticting solenoids at frequent intervals confine the radial excursions

of the beam. The basic accelerating section of th: 1 nac consists of a

linear a Tray of these resonators and solenoids within a cryostat that can

be isolated from the others both with respect to vacuum and cryogenics.

The four sections of the booster make use of resonators that

have two lengths. One type is 35.6-cm long and is optimized for a pro-

jectile velocity P v/c = 0. 105; it is now completely developed (sections C

ANL SUPERCONDUCTING t-INAC

A B C D

I - _ __ -- _ -.

- STRIPPER /-OLENOID L- SPLIT-RING/ -- HEAT SHIELD RESONATOR

-- VACUUM WALL 0 I meter

Fig. 1. Schematic of the heavy-ion energy booster.

I. At

I. Al

and D). A second, less-demanding,

type is 20. 3-cm long and is opti-

mized for 3 = 0. 060; it will be

developed in late 1978 (sections A

and B). Section C. will be completed

and put on line in summer 1978 and

the identical section D will be com -

pleted some six months later.

Cryustat A is being used initially

as a prototype in which two 35-cm

units a rc mounted, but these will be

replay ced with the final 20-cm units by

with the shorter units, vrill be built as

in 1980.

H,~ U4D.STRB,

)LME

a.1U

G I7Y-

Fig. 2. Schedule for complleti n

and use of the booster.

mid-1979. Section B, loaded mainly

soon as funding is available, p roblv I

The rather :onplicated schedcul e of cv ents outlin('d above is

summarized b 'fig. 2, which shows the va rious configuratie ns that will be

used during the ne-:t two years to accel.-rate heavy-i on beams for the

resca rch program. The advantage of having modular cryostats is obvious

from the figure; and the fact that linacs with such large changes in configure -

tion can be useful. emphasizes the versatility of a machine nade with

independently -phased resonators.

An indication of the appearance of the accelbrator s, c timns

may be judged from Fig. 3, which shows a general view of the booster a rea

during an early stage of assembly. Here section C is on the bc-am line and

section A (in a temporary location) is open for assembly, with a resonator

being lowered into position. Apparently because of the use of a widc -angle

lens for the photograph, the 12-ft long cryostat C and indeed all lengths

into the paper appear abnormally short. The new target area to bt ased

with the booster beam is seen in the far background.

Each resonator consists of an inner drift-tube assembly

made of pure niobium and a housing made of sheet niobium that is explosively

7

I. .I

'k

Cs.1

2' 1. / 3 . -

41.

X 11 ... -

st a - a s 1)1 b ':

belm i 1 cay watspe hss(Irnb; a((l1d

. 4 K 1iCpi hol ]jim wit Hin th. '_ i 1( dC rift II , nrd

heat n (-rat d in th h<.using is . pluctecd 1 I V'a 01l(d heat sink

41 iIg t.( .Op)' r ba (king of thc Wl,(n ed Iliob inm.

RI (AwEr i- fed to tin III 1r .1 Jridft -tube as s mbIy from a

1 50 -w .a tt s(Olid t - r b. f rn - 1 a lI: trom

3/8-in. , r n a .' :i : by m-1 a ns

of a high - . r volt; g( -contrLt 0- rnIc-tan (: ( ) voloped for th

puripo e. 1his de,ict', whi. is us( 0 to 1ek tht rf lias 0 f a resollatoIr

with r( t. (. t 't KE - nast(r ( V e o. La . ['sted on a

res()nat-r In a b m--lil U >f at :i nd bt sh' q I iua .

I h. design aim fer tihe 35--cm rfsn. - is an av cagoacceleratIng f1l(l of 4. 25 \1V/m, which implis a ?ain f 1. 5 >1V

(i1, . 1.5 Me' per (:ha rg") from ac h . K Th( r onators wili initially

ii V

[i-I

'I

t

t ? Ir;tt d ;t a somw(vhat lowrr field, in the rangc 3.0 to J. ' M

li(n, WhknI n-)I IrL.(?nt. t;isks hav( bE cn (omph tL(d, th i et r, ." r* (1 ti

Dl1sh the i4 l! np to tI d-sign gu:t! will b urnd rt n. h ler ti ng

1 I A t:, 2 m units i:- txHt( tod to - 1K least 10K higher (for th-

povv r di ssi,).ti>) than the fi Ii in the la rgtr units.

}.r(ison;itors a re oolI d to a ternee r .r(' . uout ". *

of flowing tw.o-phas helium in a < losed oirculating- si: m.

I ti driving pres-oi for th flowi tho rofrigeorator itself, w~iuC II

throo (G: ;>eSSors) :5upplks nominally 95 watts of cooling and a ..

of 8 gm/s at 4. (, IK. Tho cooling power c an be 1n; r, i

value by veriz nIIg tht iquid(jl (-heli um inv ntorv in a I 0-:t

d1(watr.

Supnr (onjiiuc ting sol noids a re used to limit the t r n) = vrst

vxCursions of tht beam. ht st" hb)rid magnets consist of a suptrco sa( tLan

col and a soft-iron return voke and shield. The mn a( ;,urod tak fi ld is

7. 6 Tesla ; and tht length of the (oil is chosen to give a focussing pow ,r

2P dz th 1t is st r'm .nough not only to c ounterba lance the def< n

)

I. Al

action of the resonators but also is strong enough to -flovw the average

bam size to be minimized through most of the booster for most ions.

The solenoids are cooled by flowing licuid helium in the sam e way as are

the resonators.

All of the c ryostats for the booster are end-log iling units and,

except for section A, all are of the same size . Ii each unit, the array of

reson;tn us is surrounded :. I nitrogell-(ooled h(at shield ind, outsid-

of it, ; noum vail (set Fig. 1). Even though thi' interior of the rtsona -

tors is open to the outer v\acuirm region, including the wa rn outer vacuum

walI, the pre ssour inside th1 resonators i, ext remeely low ( 1 0 Forr)

dr1i optr;ition because of cryopumping on the noter surface Af the

re sOnat(. rs.

LaCh ervo:stat CaIn be isolit from t.ie oth rs und re-m(Ivd

from the ba rn lint without disturbing the cooling or vacuum of thL tanks

remaining on line. ;)n, e off line, th, whole imnnr assemibly of an accclra-

tor section (nn be rolled g1t tht ind of tht crvost-tt, ;ind ill disassinbly is

then done in the open. Vhir s ct; is rejdy to be put into service, it

is cooled ( '"'.tn uff line, completely test, (, and fin;illy miIOv(Cd on lin' while

still cold. While the maintenance of a section is a r rid out off liin, tht

sfctiols remaining (tn line can be ustd for a celeration.

P)( th the booster nd the bunching system a r, o nt.roled

with the assistance of an 11/31 -n lit PI)P comput,-r, which a i ra cts

with C(A'1AC rates by means )f -a ri! instructions. In eI, rai terms,

ha rd- wircd cl edbaic k circuitry is us -d to co ntrol rc soariator phase ani m I -

tude on a fast timl scale, wher a tie computer i"ts the r(fi re-nc,1 vailu, s

and monitors and controls phase and amruplitude on a slow time scalt.

Similarly, the computer sets and monitors the solenoid fields. For other

parameters, such as temperatures and vacuum pressure, the computer

provides only monitoring. Arid finally, the conrputer is used to record and

analyze beam diagnostic information, and this makes it possible to tune the

linac rapidly.

10

I. A 1; 2 a

The beam from the linac passes into a small new ta rget

room that will house a 1, rye scattering chamber, an existing spectr, graph,

and various specialized re a ction c ha i bers. The layout of the ar is

planned so that a debunching/ rebhi inching resonator ;in be aided to manipu-

late the phase ellipse of the dutput beam tO icett the needs of the experi-

mretnter.

2. :-TAI'US OF T Ill PROJL(. 1

In general terms, the status >f the proje t iat the 1(nd oNIa r( h 1978 is that fabrication and testing of components is moving ahead(Al rnn fronts. 'I 1w )primnfaVr technical problem of the project, the

develop)ment of an effective supercondiucting resoiiat'.r, has been -;i ( ss-full', t 'e r< nie, and ibri( ati on pro. c1 res la Vt been stand rdized.

Almost all of the effort to d1a te his been devoted to tiht high-i resonato rsrequ: re1 f0tr sec tions (: a 1) ). During the sec (1 haIlf of 1 )78, sc 0m1e

effort will L shifr, d t<, thTl' 1, vel IIpmi t t o ! v t13 ow - iinit- req i red fo r'

sections A an( i.

The fmpha sis of the project is Iow; oni the a5isembly and

testing of complete :tcele rator sections.

a. _ rototy }? ,S nato rs

In the initial tests of the prototYpe (1-2) split- ring st rmcture

(Fig. 4), neither the drift -tube assembly nor the housing performed satis -

factorily. Because of a surface defect on the split ring, the resonate r

broke dowvn at E 2 M1 V/in; and because of a low surface conductivity,a

the housing dissipated too much rf power. After investigat ions that are

outlined in Sec. B, tests carried out during late 1977 showed that both

problems had been eliminated or reduced to an acceptable level by s irface

polishing. The limit on Ea was extended to >4 MV/m, and the Q of the

system was improved to the point where, for example, the power loss is

4 watts at E = 3.0 MV/rm. This is good performance for a linac although,

as seen below, the production-model units are even better.

II

12 I. A2b

h._ 1ro(dICtion-Mode Iligh-Lbeta esorato rs

On the basi of thy' lessons learn d from the study of the

protot}pu P -2, the bonding procerlure used to produce the housing material

was modlifi(d in Order to r (Alice the surface contamination that initially

cause rI low ) in l-2. This chang* in pr-oc'(lur was enti rely su<( essful,

1l( smurfa< e contarniin;,tiori of the housing is no longer ; signifi a nt p)roI m.

The initi;. goal for

l cT l NU! / of [ I 1 A t1 F EB 'MAN APR MA f ,JUNEOCT ~id ~ n FB MA ~ ' protlu, (torr - rnrodel re- Or;lto r- i

H-, (r ood units ( )f the se, four

-2 ., t r( vorrplted by tie rnd of

" 4 r( h I 978 and tht other two were

lit ;n< ring c(rnpl)ttion. Aln ald ltionlr;

HG * siX units ar r e soIei l(ed for ft Uri -

cati on hur ring th s- ond ha I> 4Lu

1978.

O r ope ra ting

ex p eri e with tIh )ro(ducti,>n-

model resonators Is slrinn:i(dR-)

j 1 - 1by 'ig. 5. Hlert, in the top1) ]; rt

of tie figure, the solid clots show

when the resonators weVre deliveredFig. 5. L"xperiercce with performance

of production-model resonators. from the shop, and the open circles

show when tests of fields were

carried out. The numbers within the circles give the measured accelerating

fields when the rf-power loss is 4 W. When two mea sure ents are given

for a resonator, the first field value is usually an absolute limit set by a

surface defect.

The bottom part of the figure shows the accumulated acceler-

ating voltage of booster resonators as a function of time, on the assumption

that each resonator dissipates 4 W of rf power. The dashed lines are pro-

jections of performance for the last two resonators.

I. A 2( -

C. 1;F Contr(l

A complt'ti sct of thi il(ctronics to be us-d il (riin11g .ta

(nflt rollin individilji re(sotltrs h:I b Ii 11 tested 1p to a ingi fiield I ', .

'I h rf amrlplifier, phi;s -cirnlt rul pulss r, atnd c(n ntriIl ilIctrolhi s, .11 (,f

tic h .r trull ( ( l( lop)(, wOrke(d withoutt it-ltdtio \ l-wi1 Ilsd Oil

r*sOItita( r -L.

T ht' voltag(;('- i )nt r<llll"d r't;t tainc ( \'( . ) usI' ' r ft t tllling

tpirat ft tii ' ii l1v up to the pilit hi ri it \w.s hfd1inf aL r;1(tiv. tuninmg

of ; \'A. I his p)owe r I(v(l inl)1i s, for tx:im irA , tlit thi r( s (unitOr

phi;s( is c(nt roll bh 111p to fild levI of 1 MV/r if tlt vibritlot--itldu ( ( d

rf-fr.-uI i'n y v;irl;Iti ol is 15(1 lIz. ' r <iu 11 y v.riati o al. small as 701 liz

Il.. ii i oxp)oin'Iit di t 1 til t -tt o rvost;It lsid 1etr th study Of indliVi(iu15 I

r1 5onI;t0rs Thus, %V' dxp)oct thlat thie ph;tse ("ll r<>l system'ii is nor thani

;ie p t( for the( initial ph};s (,f a c l r;lt'r oper 1.ti<>n, although w.( dI n't

,,(t }1 vi V ny :, p r I1\ ('; w'tlt( \.ith; 1 r 'C1 lue t \' vai lation11: 1 th( bt':tml-I]ine < riostats.

(. T if,.1i( ( IiitrOl System

Ih( lin c as ole \will be ( untrulle(d by a systcnm based

On a '1)}'-1 1/31 mriIc opll)-t( r. 'I he computer a(I >th(oir c components wir

dev11 r-- late Nov(mbir 1977. Th ,yston is being assemn bid, and

pirog ramimitig of som( control functions has sta rtid.

C. Cryostats

ihe cryostat for accelerator section A has been com phlted

and tested. It was found to have th,* good chiractiristics Uxpct*:d from

design studies.

The vacuum tanks for sections C and D have been completed

and the inner parts for section C are being assembled.

13

I. A2f, g; 3

f. i -lium r< efrig ratieor

'I he helium refrigterator, a CT 1.100, and the ;ssociatd

heliurn-itas storage t;mnk h;uve been installed.

1"; ri i c 1ti on of th e flowing -liquid-helium di stributi cn s% stem

is well ;jtv;an, A. A 1000-liter stor;uge riewa r that is an important pa :t

of it. systern h;8s Ieenr deliv e red.

. unuhirg 5etn

Ihe p rototype of the < OmpA)t) brinchi rig system w;s suc ess-

furlly testr(I rhiring tin first hi;lf of 1977. !his systEm consists o a pre-

indr m bri t )1 ih r, a post-t; 1(d1 n sr)er t n d1 < tinig 1)11< h r , ml ,d a Jhase

die cr I or thl;t (I\n;ri c ' 1'y links th- phases of the two brinc hers. More

(let8 il 8 hoit fhis sys tern i C give, ini Sec. V. A1;,.

I hie post -tan(derr superconlucting bu~inche r to be used with

the lina< will inrti;rlly be One of the prototvpe urrnits used in the dievelopm rnt

of the high-n reso nr;tors for sections (: ;ni I). Ihe tumpora rv uit w.l

be repl.rced by a more smit;le low-F ,(eson;tor in 1979.

. PLANS 1O1 TIl: NEAR FUTURE I"-

The irnmedi;rte goal of the project is to install both solenoids

and resonators in c ryostat A and to test the whole a ssem'rbl,'. This task is

expected to reveal any problems that might remain ; nd therefore, once

section A has been successfully tested, it will b a straightforward matter

to assemble and operate sections C and D. In the initial assembly of section

A, high-3 resonators will be used; these will be replaced by low-P units

when they are finished in 1979.

The project schedule is aimed at the completion of section C

during the summer of 1978. When section C is operational, it will be used

14

I.A3

to ;( 'elr;ttt ion beam.,, th1s initiating thu final tist of thu ifftctivunHss

of suD(' rcondu(ting-lina c t (chnOlOgy.

Th initial months of ot( r;ation will h( dvt,t i prim, rily tO

th ,,!du y o>f lina ch; ra-tu risti< s, but th- linac v.ill also b. ustd for h avvy-

ion rs a rbh to th( uxtnIit fiasiblo. Although s(t.ion C is a rilativtly sna ii

dlxir (-~ rl long), it v.i1 provide at (ast 7 MV of adclitionial a.ci hlr;tion

nid will monr thin dlotibm thu tnurgy of ions in thu mass rang( A 1;-IK

Thlis, it will griatlv ixtund th rtsea ruh ;Ijability of thu tand<i m.

l h( ompl(tion of section 1) involves nit n( v: 1 -cl.nical prob-

if-Ils, and th rate of Omlpl(ti( n (i ind(s 1)rim;lril\ wi tlihi rt.- (f r.SUOnatOr

fi bri atjiCn. !h(" section is ()xp)(ct(d to ib" OT rational by tarly 17, and

it wI imni(iat 'h put into Sur Ivi, i n r sli thi a cclratinu voltagi

of th, inac to at lha st 11 M V.

If the ;vailabl Iundis permit, thu d(\evlopiI(4nt of thi tuw-j>

risonators rICin1iredl for 'ff. tivi usu of so tion A will sta rt during thu

b((Onl half (A 1')78.

I7

16

B. INVI.STIGATIONS 0C SUPERCONDUCI ING-LINAC TECHNOLOGY

This part of the progr;irn is cone rned with ti general

aspectss of the ap]pli< ;ition of silpereonducting rf technology to the ;iccelera -

tion of heivy ions. D, ring the p;st yea r, th( choice of all work has -eendictated by the urgent (ev-loprnent;il neerls of the he-avy-ion booster project.

Nevertheless, mn;lny of th, investigations are of gener-il interest to super-

< on(ucting linac technology and some of even more general interest.

1. XlA I l.IA IS AN I) F A I<IC ATION T I A INIQU VS

A colrposite material consisting of nitcbimn sheet cxplsively

bonded to c opp -r has b en (It ;in -fI' ci nI .fw sup rconduct rig

m;ttri a.

TIhe bonded cormposit \,;is chosen in 197f; as the mn;terial

from whieh to fab)ricte the housing of the A rgonne split ring. The niobium

sheet provides the superiondlicting surface and the thick copper backing

provides a path for heat transfer. 'Iis approae h was chosEn because it

was expected to reduce f;ibri nation 1osts an1(1 to simplify the c ryogeni( design.

FLxtensive t est; show\Vecl tha1 t the bondIed material is excellent

in most respects. However, the first full-scale resonator mr;de with the

rniatcrial was not satisfactory in that it had ;a very low Q (.x107 ). Th-

performance of this first bolndled unit was greatly improved by heavy

electropoli sing, suggesting th-a t the superconducting sitrfa ( was contamn -

inated during the bonding procss.

On the basis of the a bove results, the bonding procedure

was changed so as to protect the niobium surface from direct t contact with

the bonding explosive. The resonators made front material bonded in the

new way perform very well without heavy electropolishing.

These results show that an effective procedure for tr. eating

and using the bonded niobium has been established, and the material is

now being used routinely for the fabrication of resonator housings. We

I..B1

I. B1 -3

expect that the bonded niobium will gradually be adopted for a va riety of

cryogenic applications.

2. RESONATOR DIAGNOSTIC TEC HNIQUES

Further refinements have been m-Iad(: in techniques for dcter-

mining the locations of rf power losses in superconducting resoti;It&rs.

In particular r, du ring the pa: ' year we have extensively applied trijn1gula -

tion technique that uses the velocity of second sound in liquid helium to

locate the point at which a thermal breakdown originates on tin s surface of

the split ring. The technique has been shown to be r liable end th, spatial

resolution has been improved.

B _cause of th accuracy with whi< h a rlfa t on the split ring

can now be located (~ 1 cm), it is feasible to ;itttrnpt to remove the defect

by treating ;a limited area of the surface rather than by treating the whole

resonator. Techniques for doing this by means of d'1ctropolishing have

been developed and successfully applied to defective resonators. This

suggests that it will usually be fra Bible to identify and correct defects in a

new resonator with only a moderate degree of effo rt.

3. RF-PHASE CiNTROL

The phase of each linac resonator is controlled by a voltage-

controlled reactance (VCX) of a new kind conceived and partially developed

in 1976. The control device was tested and was found to be adequate for

the control of linac resonators.

17

18

4. BEAM-DYNAMICS COMPUTER PROGRAMS

A ( )mputer program to track the paths of ions accelerated

through an indepcndently-phased linac has been developed and used to study

various questions about the dynamics of ions in the heavy-ion energy booster.

One important investigation has been concerned with the

behavior of unwanted ions that enter the linac with the wrong energy, phase,

and/or charge. Unexpectedly, it was found that essential lly all incident

ions, independent of their initial conditions, are transmitted( through the

linac without wandering far from the beam .xis, although they may not be

properly accelerated. This result can be attributed to the strength and the

large number of focussing solenoids in the boosted r. The result has two

important implications: (1) very few particles will hit superconducting

surfaces in resonators, and hence the possibility of radiation damage is

minimized, and (2) it will be easy to accelerate simultaneously ions with

several charge states, which will be useful to some experimenters.

A second investigation has been concerned with the develop-

ment of strategies for optimum accefLiration of the wanted ion species.

It was found that nonlinear effects that degrade beam quality are somewhat

greater than had been expected from the an;tlytic theory. Typically, the

quality of a beam injected from the tandem deteriorates significantly if the

spread in a phase angle is greater than about 4 during any part of the

acceleration process. Fortunately, we have no difficulty in keeping the

phase spread within these limits.

Computer calculations also showed that the linac itself can

be used to some extent to debunch and rebunch the beam in order to satisfy

differing experimental needs. This capability adds greatly to operational

flexibility.

A simplified beam dynamics program to be used to guide the

tuning of the linac is now being written.

I. B4

I. B5;6

5. ASYMMETRY IN ACCELERATING FIELD

Since the split-ring resonator is not axially svnmt cii ic; 1,

there is necessarily some as yinmne try in the accel(-rating field, and this

will tend to steer the beam off axis. The effect is most pronounced in thb

gap betwe n the two drift tubes, Wh re the a sy mm tr is in tit fo rm of a

transverse field in the horizontal piane.

It has recently been shown, from the rults of a refu il

dile tric-bead. measurements, that the transverse field is 6/o o.f the

;ixial field. Since this value is about twice as great as had origin; liy

b en expected, it was initi;atlJy feu red tha t it would c-a usci a serious detcriora -

tion An beam quality. lowt ver, further study has shown that tht effect is

Unimportant for th- boost, r be as e (1) the drift tubes art so large and

(2) the focus ssing solenoids a r s(.) strong and (1ssely spaced that they

continually return the deflected beam to thi axis.

6. SURFACE -TREATIENT TECHNIQUES

Considerable effort has been devoted to the development of

t(chnicut.S f(-r electropolish.ng the superconducting surfaces of resonators

with complex geometries. I'he objectives are twofold: (1) to eliminate

known local defects in the surface and (2) to improve the overall quality

of the surface. Great progress has been made in the first task and, insofar

as visual appearance is concerned, technlcues f-r improving the overall

quality have also been developed. However, we have not yet devoted the

effort required to obtain a quantitative understanding of the relationship

between surface treatment and maximum accelerating field. This is a major

task that should be undertaken because it would probably lead to important

improvements in linac performance.

19

I.C

C. PROPOSAL FOR ATLAS

In view of the successes in solving the main problems

connected with the development of the heavy-ion booster, as summarized

"bove, the Laboratory plans to propose the construction of ATLAS, the

Argonne Tnndem -Linac Accelerator System. Figure 6 shows the layout

of the proposed new system, which is a straightforward enlargement of

the booster and its experimiental area and which requires little new

developmental l effort.

The objective of ATLAS is to provide precision beams of

heavy ions for no clear physics res a rch in the region of projectile energies

comparable to nuclear binding energies (5-25 MeV/A). By using the

demonstrated potential of superconducting rf technology, beams of

exceptional quality and flexibility can be obtained. The proposed system

is designed to provide beams with tandem-like energy resolution ind ease

of energy variation, and an energy range compara ble to that of a 50 Mi V

tandem. In addition, the beam will be bunched into very short (~50 psec)

pulses, permitting fast-timing ncasurem(ents that can open up major new

experimental a-proaches.

A comprehensive description of the design and planned use

of AT LAS is available upon r quest.

20

FN TANDEM-

TARGET AREA I

C D

AE

- -G

i-

TANDEMi - }

Overall layout of ATLAS. New construction and nw lin<ac cornpon<nts art indic i . c3 by ;ross

n

Fig. 6.hatching.

'9 1

09RE 'AN)F~M \ A

{ k 'r~ -NA4

a QKN-

01 A

:"a nt c t A

*1~__S__'_ti=E a y MA N

PA D E G'ARCU aA A

S'p 'PER

r

ANAt;E

23

II. MEDIUM-ENERGY PHYSICS

INTRODUCTION

The work of the Argonne Physics Division in medium-energy

research continued to gain momentum in the past year with the success of

major phases of three primarily-ANL experiments at the Los Alamos

LAMPF facility. A strong emphasis in the ANL program has been placed

on establishing the major features of pion-nucleus interactions. Lven now

our knowledge is limited on matters such as the relative strength of

absorption and scattering of pions by nuclei; the mode of absorption, e.g.,quasi -deuteron absorption or absorption on larger clusters; and the extent

to which reaction products result from direct or evaporative processes.

Efforts of the Argonne group have focussed on measurements of simple

"inclusive" spectra of charged particles, neutral pions from charge-

exchange reactions, and nuclear-decay y rays. The particle spectra probe

the initial phases of pion-nucleus reactions while the nuclear y-ray spectra

are sensitive to the overall process of nuclear excitation and evaporation.

Even for the simplest nuclei studied, qualitative features of the nw data

evidence the importance of nuclear structure effects in the behavior of pions

in nuclear matter. Anomalies in the mass dependenc, of the pion-induced

proton spectra and in the spalltion yields of nuclei near the target mass for

heavier nuclei highlight our lack of understanding of the initial phases of

pion-nucleus interactions. Direct observation of single-charge exchange

has previously not been feasible because of short lifetime and decay mode

of the neutral pion. In the past year the Argonne group demonstrated a

simple and easily implemented technique for direct measurement of ir0

spectra. The feasibility measurements provided a qualitatively new kind of

data; and trends displayed in the first results suggest, quite unexpectedly,that the bulk of this reaction proceeds through a quasifree scattering process.

These studies of inclusive spectra have already provided new insights into

pion-nucleon physics and extensive measurements are planned at the earliest

opportunity over a complete range of targets and kinematic conditions.

The new data are likely to play a major role in the development of a coherent

theory of pion-nucleus interactions.

A second area of activity has been the study of elastic pion

scattering. A survey study of targets of varying atomic mass over the

region of the (3, 3) resonance using the EPICS facility at Los Alamos was

begun late in 1977. The first spectra indicate an experimental sensitivityand angular resolution which is unexcelled. The results, together with datafrom other laboratories at lower energy, will provide a complete picture

of pion elastic scattering for representative light, medium, and heavy

II

24

nuclei. Tht possibility of direct rieasurements of pion-nucleon scattering

at 180( is also being explored. Data at 180 are particularly useful in

constraining global solutions to pion-nucleon scattering. The Argonne

effort is based on the recognition that unique properties of the low-energy

pion (nannel at LAM PF ;1 re ideally suited to su. h a mea surernent.

Preparations for a feasibility experiment were begun in the past yeir

A.' LANPF experiment concerned with the transmission of

positive and negative pions in single c rvsta is was comipil-t :1 in the na st

yea r. Hitherto, vt ry little has be(tn done with negative particles. The

experiment was carried d out at the El:l(,S th;tnntl using very precise

techniques for determining channeling behavior. Steering of the pions bythe channeling c ryst;tl as well as anoi;li-s in energy loss were observed.

From these data, it is clear that important phenomena take placu( in this

new r egion of pa rtic le - solid inte r; etions. A r gonna e pa r tic ipation ( o tinmtd

in th, I ,AM iJ c oll;lbor tion on measurem(ent of double -c ha rge ex< hange of

pions. I his uniquly m esonic re action has been the subject Of much

theoretic a;1 spec t il ;ti i n. A subst;tnti al body, of d; ta wv:ts collected in the

past yea r and discussions between Argonne expri-imnenters and theoretical

staff led to nw theoretic "tl ntlderst;tnding( of this fi; 1 tt of plitii-n(c1(lI1s

reactions.

. Gainna - Pay Study of Pion-Induced k.eactions on Comup ltx Nuclei

11. 1'. Jackson, S. B. Kaufmnrn , 1,. Myr-Schltznwister, J. P.

Schiffer, R. 1K. Segel, S. I:. Vigdtr, l,. L. Rutledge,t N. L. Burman,P. A. M. Grat, R. P. kcr wine,4 Ml. A. Ytes, ;tnd S. L. Tabor

The spect ra of residual nuclei produced by pion-induced

reactions with nickel isotopes h,1ve been studied using r and - beams

at bomb rding ,nergie s of 160 X1eV and 220 MeV from the tow -energy-pion

-:hannel at the Los Alamos MI eson-Physics Fa cilit': . Resid ut1 nuclei

were identified from prompt gamma-ray spectra generated by pion bom-

bardment of even nit kel-isotope targets. Induced artivit Was a Iso

measured for a 62Ni target. The observed prompt gamma rays typically

account for -I/2 the total reaction cross section. For 6 Ni the total

observed cross section is 890 mb, exclusive of inelastic scattering.

Chemistry Division, ANL.

tNorthwestern University, Evanston, Illinois.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

lIIa

Fig. 7. A historam dis- /

play of thi t ross s e -scc 5 ~Otions for production of

final nuc lids from 220- /- 62 co y . F. 6U

Met n n uf iNi. The/ '

resIlts of bth promptand delvid ' m;asure- v -

m(nfts 8 re incl' dt(1d in -

this figur . -.

The pion production cross s, ti n s of individual : I f 220-

f, 2Ml t V pions iucidnt n />2Ni ar, shown i FiL. 7. -

yields of rtsidual nuclei 1r( a smooth fun< , lw , for >N Ni obta ins

a total cross section of '1200 r, close to the gtomviitric cross S'c ioI.

F romn these da to and th OSe from a ')revious run, t nurmhr of systematic

ff(uct s become ppar, tit. Of o rti ular note a r: (1) -xc ipt at pion

enr< i( - 50 NieV, th( spe( tra are vi :tw lly indt pnidwnt of pion( char

r1d (Iner , (2) th .v("r' i- ii be r of nucleons rt uo. , increases with

incr( a sinV di ut; 11ce of thi toi rot nucleus from t;. line of starbilitv, and

(3) thp n/p rtio in th, r nmovedl nli1( oris, while in'snsic iv t<- t . ,!lw

4 th( incid.t 'Y1(,in is quite sensitive to thi t l ron \ . .. :

is expected to proc< ,d through a pr(-tquilib -ium ph i t ' Ilih "st

nu('le( ns :1 r, 'mitt'-d, wed by n (vaporation h"s- i: u ch the

residual excitation emnrgy is radiated. Several f< <tures of the data are

most likely ; ( onseCunce of the evaIporation phase amn thwse appear r to be

satisfactorily understood. Howtve r, ;ts;e ts of the rea Ucti who

sensitive to the pre -cequilibrium phase, such as the anitmt of .ne rc.

apparently availa ble for evaporation or the rartio of pin bsorption to

scattering, are not readily explained. A comparison of the data fr bi

with predictions of an intranuclear -cascade calculation shows that ,-Ii'

II. a, b

yields for nuclides far frrn the target are reproduced by the c;iscade model.

The discrepancies for yields corresponding to AA <6 suggest that our

current understanding of the pre -((juilibrium phase of pion-nucleus

interactions is inadequate.

b. Study of lion Absorption Mechanisms in jle and Othe r Nuclei

11. 1K. Jackson, K. EK. R ehm, L. L. P utledge, Jr. , J. P. Schiffe r,P. I. Segel , 5. L. Tabor, and .M. A. Yatest

Vvei though pions a re one of the basic buil(Iiing blot ks of

nurcl(ar matter, our unde rst;inding of how pions propagate, lost enli.rgy,

aid get absorbe(l inside a nucletis is still v- Iy ind; qu( t. T( obtain

.xperimental information on these processes we have stwdie(1 the energetic

protons produced when pions are incident on nuclei 1. Using tih LAM\iF1~_

L1P < hann(el, prt oris produecdi by 60, 100,+ - 'I

and 220 MeV rr and n on ta rgets of He,12 62 181

- 7M(. C, Ni, and Ta were measured at

I V5An 90 . Th(" dIat; on I Ie v,(,r(

sp"ciailly inforrn;tive. A m ,a sured

--' sp(rum 1s shown in Fig. 8. (lea r

evidence, in the form of a distinct pe;ik ofIi "

- - high-conergy protons, was seen for a two-

body absorption mecha nism in which the

pion deposits its rest mass and kinetic

energy onto two nucleons. This mode

be comes relativeLy much weaker in CFri (Mes/)

and heavie r nuclei. Evidence e is also seenFig. 8. Proton spectrum at

4ig. 8.frot spectrm+ at for a possible multinucleon-absorption450 from 220-MeV + on

helium.

Northwestern University, Evanston, Illinois.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

1H. E. Jackson et al., Phys. Rev. Lett. 39, 1601 (1978).

26

II. b, c

rnode in all n'i lei. Further rneasurernents are planned in ,rdcr to study

the angular di stribution of protons and the b(hd vi( r (A the inelastic .h.-trged

pion 0(i1ld.

4C. Properties of Inclulsive (e ry ) Heactons in Nu clei

T., J. x14es 1. 1 . G(.cs-tmlan, l., . Holt, !1. !' . Jaickso, 1. '.1.

l aszewk'ski, P. P. kedwine,4 ;t nld i. A. Yate.-- il1iam~s

While singu.e -charge -ext hatge pion re-aetiris a re recognized(

as a promising probe of pion-wlel(ieus intfr:lrtions, the di!fit. ulty in cetecting

n's with any precision hfts pre'enWte d ext enIsive sttrlies. We have iegun a

.:tuid' of Whe (Tr ,n ) rea< tion at 1() M teV using a back -. eI gle-gaevis

te hriqi e, ba scd on the large Dr.ppl r shift of elec V 1)l torns et !tted in tht

batk .l;w rd dire tinn. I w,u eay photon> : re bs( ev 1d in (oi CI t.cnt.'ct in

t dte tor ,tir consisting of a large volinme I N(l( I 1) t ount. r ;ind Pb-glass

h-ower count er positionedt 1 i( a;it. he easu irlnts wc ' I .

tit (in the 1("%,-t ne(rgW-pion ((h.Onniwl of LAMiIIV asing Ilixes of ~2 - 7

C) 12 1i, -2j8pion/s. Targets of Be, 0, (, :i, and 'Owe re >tui t d.

M ieasiremin(ts hav- been rinade at 4.( :c 120( A typical result, f111r O

is shown in Fig. 9. It is evieieit from the sp1)ettr. that most of the n-nucleus

charge e'xch;ni( favors large' monuentiun transfer. Ithe observation that

the 1. iiflerential cross sections peak near the nomentuiin tr;u:t. r

appropriate to free nuclear reaction suggests a qjul li-fri tLe. ot s( ;itter -

ing. A si:nple calculation of quasi-fr et scatter ring by a n( utrun-pr,)ton

fermi gas reproduces the shape of the 120' cro.s (- tion very Weil. The

energy spectrum observed at 4U suggests that T"s (;t er'tl at the t rwa rd

angle are most likely the result of a process more complex than qu; si-fr

single-charge exchange on a single nucleon. However, for all targ ts the

angular distributions integrated over n energy are peaked in tht. bckward

direction with do-(120 0 )/do-(40 ) 3. The observed mass dependence is

close to that appropriate to a surface reaction, i. e., a- A2/3

Los Alamos Scientific Laboratory, Los Alarnos, New Mexico.

T. Bowles et al., Phys. Rev. Lett. 40, 97 (1978).

27

II. c, d

. *20'. . r0?

- 50 10" Fig. . ifferential cross

E Y; section for single charge* - L T~iLJexchanges by I60 at 400 and

w T~ 'Mel) I 1200. The inset shows the

c russ-section shapes caI( iu -

1 41 1 _ated for (ha rg -xchangeb

f Is atte ring by a Fer m i gas.

80 200

T (Mel,

+ rjMost prcviou s discussions of (Tr ,, ) rca actions have

n oh; sized Ow mornentumn transfer viewed in terms of optical model or

coupled channlI processt-s. These processes would be forward peaked,

proceeding mu; inly th rough the pop ulatiflon of isobaric anAlug states. The

observed backward peaking together with a broad Tr" ene rgy spertrun is

ve ry different from this picture. A Nl\ontc Ca rio cal ulation of cha rgi

exchange on Ni using the code V EGAS predicts a spectrum at 400 dominated

by near-elastic events and is not consistent with the observed sp(-ctrurn.

d. I)ouble-Charge-Exchange Pion Reactions

R. J. Holt, B. Zeidman, M. P. Baker 7 R. L. Burman, M. D.

Cooper,' I. H. Hieffner,' D. M. Lee,' R. P. Redw-ine,' J. E.Sprncer, D. J. Malbrough,t T. Marks,t and B. M. Preedomt

Further studies of pion double charge exchange (DCE) have

been performed on targets of Be, 12C, 24Mg 26 28 40Ca, and 58Ni.

These (n , T ) reactions were induced by 140-MeV pions from the LEP

18 + - 18 16 + - 16channel at LAMPF. The results of the O(T+ ,Tr ) Ne and1 O(+ ,Tr ) Ne

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

tUniversity of South Carolina, Columbia, South Carolina.

II. d, e

reactions have been published, as has a theoretical c xplan;,tion e)f the. ross-0

secti')n ratio which is based upon nuclear r-structure effects. l'he 0 cross

sec tions measured recently range from 150 nb/sr for e(rr , rr ) (~ to

12 + - 121 b/ sr for :( rr , r ) 0. The measured variattions ill ross sec tionf

appea r to be st rongly cor relay ted with nuc lca r-st rit turte effe ts, bet

unc ert;tinties in reaction theory at tIhe present time make it difficult to

extract 1e finit iv information rega ring nuclei r wvrtv functions. For the

410 58heavier targets, - Ca and Ni, only upper limits f 300 nb/sr were

found for the u ross section. rXc reactiAnls tn 1 th ell nut lei as well t

S i nluced I )( . are planned.

. ,;et'e ring of_ Pions by C.onml ex Nuclei

1). F. C esimrnai , C. Olnier, B. i.eichneA n, C. E. Buirleson, 1.I)evere1x, . L. !Jc (drit (, . I . Morris,' 1. A. Thic .e t. .Se'iel, { . I , Siem s. t , enc 'A'. Swenson,

The eistic( and inelstic scatte ring of both r and TT by BPe,28 58 20:8

Si, Ni, 1 nrd Pb has been studled at , 1(2 Mt V. The angul;r0 0 + () 0 -

rang, investigate(I was 14 to 110.5 for TT e1nd 15.9 to 94.2 for TT

This experiment, the first sc( l',led, was performed with the IHICS

spectromnet('r systei et LAM I1. Thws data arc part of a survey which

will iruvde the systematics of pion scattering fror complex nuclei at

ene rgit s sonm ewhat below, on, and above the. (3, 3) resonance observe d in

r-nucleon sc;t tte ring. Except for Be whose minima are damped, the

angular distributions for elastic scattering at 162 MtV (the resonance

energy in nuclei) are characterized by extrernev strong oscillation: whose

frequency reflects the mass dependence _f nucler radii. Over the angular

New Mexico State University, Las Cruces, New Mexico.

tUniversity of Colorado, Boulder, Colorado.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

KVI, Groningen, Netherlands.

11Oregon State University, Corvallis, Oregon.

?q

30. e

\r

..

I,I,I"

12J

1'-i

.I,

Fig. 10. Aniular distribu-tions for the elastic scatt

ing of 162-MeV Tr by 9 BeSi, 5 8 Ni, and 2 0 8 Pb. Thsolid curves are optical-model calculations utilizi

parameters obtained from

electron scattering, whil

the dashed lines result

from calculations with

modified radius para-

meters.

range studi.r, the diffe-rential cross sec-

tions vary by about six ord( rs of ma gni -

tud . IneLastic sc;tte ring to collective

states is also obs( rve(d to have strong

a ngila r oscillations which ; r- < haracte r-

istic of the anguLa r momentum transferred.

Opti: I -IIIdAI" c-;l<:ul1tions

for the elastic scatt ring have been p r-

formfd \withi the motntum-spare cod

H11)T. I he (ollision nmtrix is < ;l 1;ated

using free pion -Mu leon pha;se shifts arnd

a mod-b for off-shwll extraplJOIiatiOnl.

Nuclear r matter distri botj(jns% w(re ;rssurmed

to be of the Woods-Saxon formi r ith

p;ram(-ters h riviri from h ctron 51 Btter-

ing. TIhe calcuIltions a r( cormp)a red to

(kt' in Fig. 10. fomt1 'whiat bett r

B gre I ent with th' locations of minim [l;r

;a re obt;uined with modified r;udii R ,as is

' also s(1n in the figure. For the nuclei

studied, no substa ntia l difft rc'nces

between netutrn ;,nd proton ralii ar

indicated in this an, \lysis. A more com -

er- plete des( ription of this work has beene,

>:iblishc c.

I're liminarv an;alvsis ofng

the inelastic scatte ring to collective

e states using DW BA program ms yields

deformation parameters that are consistent

B. Zeidman et al. , Phys. Rev. Lett.40, 1539 (1978).

30

5

II. ,f 3

with values obtained with other reactions. Additional a nalyses involving

compa rison of calculations performed in morwnturn spai with U alc(' ulaitions

ptrforrnt'd in itonfigur;ition spate are proc-eding, Simik, r se :t ring data

obt; ined rec tntly at 1E - 291 \1 "% ;ire also being .nalyz(ed.Tr

f. Low-lInerg. Pion Ila stick Sattering from the Proton and Deuteron at1800

P. J. Ilolt, f. }.. Jickson, Jr. R. \. I,'szw ski, J. R. Spe-Cht,

B. idmnan , N. L. Burmin, 'Ind J. 1K. Spencer

The goal of this experiment is to observe, the tntrgv

udependence of th Tr -p ;ind T-d cross section; at a settering angle ~f 1,) ,

throughout the erH'rgy range 30-150 MeV b- usii Ili, niquc feature of

the lovw-energy-pion channel (IJ'.P) at thi l.os ;\'m- 1sou lhysies

Fa< ilit . In addition, we hope t) obser the tinsor polarizAtion of the

cltiuti ron at 180 in Tr-d elastit s att ring. Th.e ;dv;intagts of studying these

pion cross sections are manifold: (i) the spin-flip arnplitudes vanish at

180 and the theoretical calculations a re greatly simplified; (ii) the calcula -

t d Tr -p ros- sec tion at this ;angle shows , high sensitivity to tht r-N

ph;iast shifts; (iii) Rinat and ihomas and Gibbs ha ve shown that Tr-d la stit

suattiring and tensor pula rization at 1 80 is sensitive , to tht D-sta te

a dmui xtu r in thf deuteron wave fun action; and (iv) the C oultmb effer ts are

at a minimurn for 1t80 sa ate ri ug. Sin ce the LE7P chaein nl was not designed

with these specific mca surements in mind, a fea sibil ity study must b(

made. Preparations are unctr' :ay fur in situ fea sibility tests to b- ki rried

out late r during the yea r.

Los Alamos Scientific Laboratory, Los Alamos, New M exico.

31

II. g

g. The Channeling of Tr Mesons

1). S. GemmA11, P. IK. 1holland, C. L. Morris,' W. J. Pietsch,A. J. Ratkowski, J. P. Schiffer, H. A. Thiessen,* T. P. Wangler,J. N. Worthington, and B. Zeidman

We have m (;isured the channeling characteristics for 70.5-

MeV and 225-MeV nr and -r traversing a 120-u-thick Si crystal. The

"Xperiments were performneel on the E 1PICS channel at LAM PF. The

silicon ta rget crystal was used also as an energy-loss d!etector. For these

measurements, the defining apertures in 1. PICS wer, ;topped down to

produce a tightly-coll imat(ed pion beam at the crystal. 1 he counting rates

were in the range 10 to 100 pions/s. Tihe beam -spot size at the < rysta

ta rget was 8 mm ;< 8 mm.

Before performing the a(tua l channeling neasurement s,

we used an arranogenent containing a slotted scintillator and; a helica t-wire

proportional chamrober to measure the dispersion and other optical proper-

ties of the pion beam. The vertical dispersion was found to be 0.57

rn ad /mm and there was no deteta ble dispersion in the horizontal plane.

At any point on the target spot, the an gala r Ii ver gence of th( beam was

less than 0.5 mrad. (These measurements verified that the design chara( ter-

istics of EPICS had in fact been realized.) Throughout all of our work at

EPICS the beam spot size and stability were monitored with a "4-jaw"

arrangement of movable scintillators.

The channeling measurements consisted of determining the

energy losses and the scattering angular distributions for transmitted pions

as functions of the incidence angle with respect to the (110) axis and the

(110) and (111) planes of the silicon target crystal. The incidence positions

and scattering directions were determined with specially developed helical-

wire proportional chambers with a spatial resolution of 1/3 mm. The

silicon crystal was cooled to 60C and was held in a 2-axis goniometer

remotely controlled by an on-line computer located in the ANL Physics

Division's trailer. The counting electronics was also contained in the

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

32

33II. g

trailer. The cable run from the trailer to the experimental apparatus was

250 feet. (A trial experiment using the trailer and goniometer had previOus-

ly been conducted with 15-MeV protons at the ANL tandem Van de Graaff.)

For n , the channeling measurements showed t reduced

energy loss (about a factor of 2 for th( axial case, and a somewhat smal]er

factor for the two planar caseF' and a pronounced "steering fflect" as th

angle of incidence is increased with respect to a cha nneling direction.

The angular extents of these channeling phenomena and the effects th.Is lve s

are consistent with extrapolations to higher energies of results found

previously using protons of a few MeV. For r , there wa s found a slight

(- 10% ) increase in the energy loss. however, the m-asuremnents r(v(aled

a v' Fry large steering effect for axially channeled rr and no mea surable

steering for planar channeled Tr. These results are strongly indicative

that for the axial case, there is a high probability for negative pions to be

captured into classical trajcturies in which the pions spiral around the

rows of atoms in the crystal.

III3

III. HEAVY-ION PHYSICS

IN TR ODUC TION

The Argonne tandem accelerator is th( principal heavy -ion

facility used by the Physics Division. During the past year this accelerator

has undergone a major, and completely successful, upgrading that changedits capacity to accelerate beams of heavy ions by very substantial fi ctors.

A superconducting energy booster to this accelerator is almost completed

and will start functioning during 1978. Meanwhile the cur rent resea rch

activities span a variety of topics.

The study of heavy-ion fusion reactions has continuv-d to be

very fruitful. Fusion is the probability that two nuclei, when they collide,will fuse, and stick together on a time scale long c:0omnp1T red to the collisiontime. Two new effects have emerged from the wo>rk at Argonne. One is

the observation of resonance-like phenomena in a few ver y tightly -bound

symmetric systems. These provide a hint of a link between gross reaction

properties and nuclear-structure effects. The second new result is an

unexpected dependence of the fusion p robability on the details of nuclear r

structure within the fusing nuclei. The ramifications of these phenomena

are being explored in other proc ss(es, so far principally the ela stic and

quasielastic reaction modes.

The careful systematic study of other macroscopic featuresof heavy-ion reactions is being continued. The relation between competing

direct-reaction channels is investigated both for different target nuclei and

at different energies.

The high-resolution study of inelastic scattering has produced

a set of data of unique quality. It is proving to be an interesting testing

ground for the indirect effects of strongly-coupled channels in direct

reactions, and tends to confirm the qualitative picture that has been

evolving from the study of the more macroscopic features of direct processes.

The investigation of high angular momentum states is one

of the major frontiers in nuclear physics. An important advance in this

field came in the discovery by a Danish-German-US (Argonne) collaboration

of high-spin isomerism-a feature of nuclear structure that holds outconsiderable promise for the future and has great potential in connection

with the pulsed beam of the superconducting linac energy booster.

35

III. 1

An import; snt activity during this period has been the design

and pa rti al implementation of an experimental beam line to ca rry out re-

sea rch with the hea vy-ion earns from the superconducting energy booster.The initial beam, line will be at 00, requiring no bending magnet after t heline sections. Tt is d'signu'd to have ca refiully ccnt rolledl optics in order to;lhow foccising of the beam at any one of four potential beaim stations alongit. The vacuum systci is designed to be free of organic contaminants,in ordt r to redm e p roble ms associated with ca rbon conta m i nation. 'I he

beam stations will be oc< upied by a 65-in. scattering thimbcr, a single-arm

chainbe- .uita hle for siniltaneous cha rged-particle and n cutron time-of-

flight measurenients, a gamrnma-ray multiplicity c ounter and a He-jet system

for the study of dlcia yed radiations. This set of expe rimenta l stations will

allow for .s strong initial program in heavy-ion resea rch on the super-

conducting linac.

1. I-USION ClOSS SECTIONS

MV asureniellts at A rgonnle over the past two years haveestablished a large body of lata of fusion (ross sections for some 16 differ-ent niuclei r systems. TIhese high-pri' ision data; explore the energy aindnucl us do pende nce of the fusion c ross secti on. 1 wo sifgnificant resu Ltshave em (rged. One is a resonance-like behavior that is still seen in only

three systems 12C + O and 12 ( s 12:, and in the last yOW r in I6 + 6

The o ritin of those resonances and theij

I PRrJFC

1200f

I IL

-oo-

r relattion to nuclear structure

continues to be one of the moat

interesting Iroblems in lev;tvv-ion

ph\ sic -.

'Tle he r featu re is

,xh t serm d to be an ap pa rent shell

effect in the saturation value jf the

fusion cross Sectin I)r1 fu infus

the past year new data on 1 2 + 1+ 5 N

cnst this simple effect into s-m4

doubt a nd at pr sent the va rit itioins

il this quantity are still being

explored. The present status is

s 'un -imm rized in Fig. 1 1.

Fig. 11. Saturation value of the

fusion cross section with 160 or

12C as one of the fusing nuclei,as a function of the atomic weight

of the other nucleus.

36

I" 4

": 1

1

0

? cK I

III. la,b 37

12 15a. Maximum Fusion Cross Section for C + N

D. F. Geesaman, W. Henning, D. G. Kovar, K. E. Rehm, J. P.

Schiffer, and S. L. Tabor

NMeasurements of thu total fusion cross sections as a

12 14 12 15function of incident energy for C: + N and C + N in tht previous

ImI axyear had established that the maximum cross sections, fs , were

-980 and -1150 mb, respectively. Th latter value is '150 mb la rger

than the values obtained for oth er 1p-tshell nuclei and up to now is the cletr-

in1i xest counter exam ple against a shell eff.(c t in o . Becau se of its impor-

12 1tance we h;vt remeasured the (:+ N fusion cross section in the region

of its maximum value and have a lso analyzed the Z distribution of the

eva po ra tion residue s. 'I'he previonusly reported c rOss section ni magnitude

is reproduced within trror bars. Ihe Z distribution c omnp:ires X.tll with

the rtlativ vi- lds p redicted b'; the evapo ration code Cascade and, in12 1.1

comparison to C + , gives no indication of why this total ' r5 Ation

is uintmsual k I high.

12 13U. .\l asuirtmnt of tht- C + C JFul n Cross Section,

I). lF. Gesaman, . tniing, I). G;. Kovar, 1.: . R m 1 . I'.Sehiffer, ;lnd S ! Labor

12 11 12 15 12 10Studi-s of the : + N, C; + N, ( + 0, and

12 18C + 0 fusion cross sections suggest that the nmaximnum VaIle of the

fusion cross section is sensitive to a neutron excess of one of the nIc lei in

13 12the entrance channel. The C + C system was studied to farther explore

this effect. A 12C target (50 pg/cm2) was bomnbarded with 13C ions from

the Argonne tandem. Angular distributions were mneasurtd at E1 ( i _)lab

19, 36, and 52 MeV, and an excitation function was measured from it to

52 MeV in 2-MeV steps at 0 = 50. Yields were extracted for , hilab

P. Sperr, T. H. Braid, Y. Eisen, D. G. Kovar, F. W. Prosst'r, Jt .,J. P. Schiffer, S. L. Tabor, and S. Vigdor, Phys. Rev. Lett. 37, 321(1976).

III. Ib, c

Y4 0 SOMIUM M Y . I3 2u

Sr L UOPN I" NEON

Fig. 12. EKlc mental yields of the evaporation

residues from the i 3 C + 1 2 C fusion reaction.

For Ecm. < 17 MeV, the Na and Mg yields

E 'yM could not be separated, and thu total Na

204+ Mg cross section is shown. The nitrogen", cross sections we r': :always less than 20 mb

and were not plotted.

0 5 ;; ,5 -Fc m (Me,

element with Z 7. The resulting elemental cross sections a'e' shown in

Fig. 12. No sign of the oscillatory behavior that is characteristic of the

12 12 1 12 13 13 12C + C system was seen for C + C. The C + C total fusion

12 12cross sections were ~50 mb larger than the average C + C cross

sections at all corresponding center-of-mass energies. The maximum

fusion cross section was found to be (,0 + 50 mb, similar to that in other

lp-shell systems. The effect of the extra valence nucleon seems to be

(i) to damp out the resonance -like structure of the 12C 12 C system and

(ii) to increase the total fusion cross section.

16 16c. Structure in the Fusion of 0 + 0

D. F. Geesaman, W. Henning, W. Jordan,: D. G. Kovar, J. V.

Maher,* F. W. Prosser, Jr. , K. E. Rehm, J. P. Schiffer, andS. L. Tabor

Earlier Argonne work has demonstrated a pronounced oscilla-

tory, resonance-like structure in the fusion cross sections of two systems,

University of Pittsburgh, Pittsburgh, Pennsylvania.

tUniversity of Kansas, Lawrence, Kansas.

38

III. 1(

16 12 12 12 60+ 160 FUS ONO + C (Ref. 1) and C + ( 1400

(N tf. 2). While no otht r systems ha ve1200-

demonstrated such behavior, tht -

16 O> 16 1000-O+ O system is an ideal candidate. i

The experiment is difficult sine, 800E I

compound tart A must be us ed. 4The 4b600

measurement was finally ca r rid wit

using Al meta1 nd Al 0 ta rgei , 400-

using a subtraction p ro edur , (1 200-

introducing extensive liquid nit r. 4g

trapping to rtiduce buildup of ta rbon 5 20 25 3 35

Ec m. (MeV)c t inilation on thI t arg, t. 1h

i , I ,am Mount of ca rbon was ont inuou sly ig. I . + ( tot -1 fusion

monitored throughout the measure- cross s, tilns.

mlelt. Th h ood ;12renent betwttei

U) 27thi Si nul~tfrui -me;asured (9+ \l fusion (ross sections ,ino priJ viou1S

C)+ 7Al fusion med suremtnts ensured that th suibtraitioin pro< edure

wIs ;pplitd < orrtly. Th V 0 + 1() fusion cross Section (Fig. 13) does

exhibit osc illatory tructur< ; a p-riod similar to that seen in other

systems. I he olar structure imlpli ;Itions of l se resonances remain

to be u;-rstoucd. Ihe maximum 1s1<>n cross section is q75 t r, :is In

other 1p-shell s\ stems.

P. Stber r, S. Vigdor, Y. Fisn, W. I inning, ). G. Kovar, T. R. OPhelian(1 B. Zeidnian. Plhys. R v. Iett. 30, 405 (197().

7

P. Sperr, T. Ii. Braid, Y. Fisen, n. G. Kovar, F. W. Prosser, Jr.,J. P. Schiffer, S. L. Tabor, and S. Vigdor, PhNs. Rv. Ltt. 37, V(1976).

39

40 III. Id

d. Measurement of Fusion Cross Sections for 16 180 + 24, 26Mg

Reactions

S. L. 'labor, 1). F. Geesaman, W. Ilenning, 1). G. Kova r, K. 1".Rehn, and 1. W. Prosser, Jr.

I a su rem ent s of the energy d(pendence of the total fusion16 24 18 24 16 26

cross section fr (E:) for the 0 + Mg, 0 + Mg, and 0 + Mgfus

systems over th( energy range 30 MeV 1; b 81 MeV have been com -

plcted. Thes( iiie , surtmntnts were perfo rmed to investigate the impor -

ta nce of ta rget. deforna tion and entranm( e-channel effects on tht distribution

of reaction strength mnd in p rticula r the fusion strength. Our mrea sure-

mernits show that tthe three systems studied have o f(I.) behaviors whichfus

a re very similar except ,t. the highest energies (i.e., 1' 70 MeV),16 2() 18 24

where the (E) for the 0 + Mg and 0+ Mg systems saturate atfus

16> 24values approxima tel y 100 1nb higher than for the C) + Mg system

(see Fig. 14). An;Ayses of the results in the framework of re;tction mud(is

show that the observed (f. (1') imply anioma l ously la rgc (~1"'0 ) differ, rtcts

in the inttraction-ba rrier radiii. Moreover, the observed absolute < ross

sections are sma ller than expected at the lower bombarding energies.

Whether these fe;ttures are duc to target and/or entrance chAtnel effects

Ec. m. (MeV)

1500 50 40 30 25 20

S1000

Fig. 14. Fusion cross sec-

tions for the 16g,24 180 4 24Mg, and 160b 0O+ Mg I 1Q

500 I' 60+ 26Mg 44 + 2 6 Mg systems.

180 + 24 Mg

S

0 L. I _f0 0.02 0.03 0.04 0.05 0.06

I/Ec.m. (MeV)

III. i d, e

needs further study. To investigate this question, fusion metjsurcmcnts

for the 5N + 7Al system have been performed and are being analyzed at

this time. To obtain a complete picture of the di :tribution of re(;t tion

strength, the quasielastic channels (^ 300 mb) for tI, 0 + 2-Mg system

have Also been measured at 1E = 72 MeV using a time -of-flight .E1-Ela b

telescope and arc being analyzed at this tim. Future measurements for

the three system s .r being planned at higher energies.

12 24C. Krn ergy Depndenc e of Total Fusion Cross Section fur ( ( + )

K. Dannshvir ;nd 1). G. Kovar

We h-'.'t n -tisureri the total fusion cross section and L stick12 24

scAttering in the energy rainige of 1: 20-60 1V, for ( + Mlab

(Fig. 15). The rn~easurements were

pe rfi, rme d using the 70-in. -' ;ttte ring

ch mtrnber ;ind ; g;us-ioniz;jtion

hambr-surface-bhrrier silicon 2detector (AE -I;) system.

The results of a 'lissi-

ca l calculation (3ass nodel) are

shown in Fig. 15. The pridirted '

, (E ) are in rather good agreement -

with the data for this system while

for the 16,180 + 24,26Mg system the

2 O - -L......L. - - -- - 1agreement is much poorer. The 'o2 0.04 006 0.08

R. Bass, Phys. Rev. Lett. 39,265 (1977).

2 Fig. 15. Total fusion cross sec-S. L. Tabor, D. F. Geesaman, tion as a function of energy.

W. Henning, D. G. Kovar, K. E. The solid line is the total reac -Rehm, and F. W. Prosser, Jr. , tion as it is predicted by the

"Complete Fusion of 16, 180 and optical model. The dashed24 , 2 6 Mg," Phys. Rev. C, to be curve is the result of the classi-published. cal calculation of fusion using

the Bass potential (Ref. 1).

41

III. le, f

total rea ction c ross secti,)i s shown in th figure were established by

optical-model fit to elastic scattering data using the program Ptolemy.3

To more omplet(ely determine the behavior of u- (1.), measurements atfu s

high)e r tne rgy arc planned. The present experiment is the first of a series

of me asuremnents to study in detail th. distribution of re.iction strength12 24

and the reaction mechanisms involved in ( + Mg system.

n. H. Gloeckrie r, M. 11. Mac fa rane, and St'ven C. Pie1pt r, Argonne

National 1Laboratory Topica;l Report AiN .- 70>-11 (1976) (unpublished).

16 40f. Nuc leuS -Nucleus P otential for the () + C,: System

S. 1-:. Vigdor, 1). G. Kova r, }'. Sperr, J. Miahoney,.: A. Nt 1n laca-

Rocha , (:. Olme r, 1nd M. Zisman-

As r('portdtl l ast dear, (lastic - setternig angular distribu-16 10

tions ;11n( t ,tal fusion crss sections for the 0 + (:; reaction have been

1 6measured at several energies over the energy ra11gt 10 MeV\ 1 K ( 0)

lab211 NeV. hese results establislhtri the distribution of reli tion strength

;s a funrution of bobnarding energy an.i providt- one f the best examples

to date for testing rta(ction niodcls proposed for relatively light systems.

Among the most important ingredients in any reaction model which hopes to

describe the re;a tion processes in ;olved is an ac ratee description of the

nucleus -nucleus potential. In this year, analyses have been performed which

us sinmulta nously the elastic scatter ring and the fusion < ross -section

energy dependence to give information rega rding the nucleus-nucleus

potential. These analyses have showni that the elastic-plus -fusion data

place tight constraints on the real potential V(r) and provide a stringent

test of model predictions.1 Analyses for other systems are in progress in

order to investigate the mass dependence of the nucleus-nucleus potential.

Lawrence Berkeley Laboratory, Berkeley, California.

S. E. Vigdor et al. , Bull. Am. Phys. Soc. 23, 615 (1978).

42

III. 2a, b

2. SHELL EFFECTS AND RESONANCES IN ELASTIC SCAT'l EKRING

The observation of shell effects and resonances in lightersystems seems to be best defined in the most tightly -bound closed-shell

nuclei 12C and 160. There is some evidence for similar r inuoimaties in theelastic scattering from these nuclei of alph;t pairtiles as well as 12C: and16> nut lei. An effort was made to explore this behavior -fn (a isotopes

(where shell efftt ts have been known for some time in n -particle scattering)

with 12C projtctilIs. tiN:w data indicate definite evidence for shell effectsand possible t'\identt b)r resonances, althwilgh both the a tI t' 1 <-

sm;it r than in thlt light r systems.

12

i. KIastic Scattering of ( from Ca Isotopes

T. R. Renner and J. P. S< hiffer

The forwi rd-a igl elastic st atter ing of 12 4on 2,8Ca

at :- 1 eV wAs extended to the region bttwtein 75" and 110 (c. m. ), where

the cross sections are verve low. The results reinforce the previously

obse rved difft rtnces between Ca and '4248 Ca targets suggesting a strong

dtperndent c on the v;ilence nut It ons of the ("a isot>J)e. lt, us5(lLtti< n I

the angulai distributions seeni with 5a :tIt Ii weaker with th t rt\!r

(; isotopes indicating a possible increase in surface absorption.

40 12b. (;t 4- C Back-Angle EKl1;stic - Excitation Function

Dag I lorn, Gordon Ball, T. N. Renner, and J. . Schiffe I

In view of the recent observation of resonance-like behavior

in the batck-angle scattering of 12C and O from 4Si at Brookhaven, we

have undertaken a similar experiment on 12C + 4("a at the Chalk River

40MP tandem accelerator. An excitation function of Ca tlastic- ll\v -atterd

12 ofrom C into 180 (c. .) was measured between 130 and 150 MeV (lab)

by detecting the recoiling 12C using a magnetic spectrograph and a _\l:

proportional counter with a delay-line position detector. Oscillatory

Atomic Energy of Canada Limited, Chalk River, Ontario, Canada.

413

III. 2b, c

structure with a 2.8-Mi eV period was observed, but its magnitude was

-41 10 in (/-R ,thf d about two orders of magnitude less than in

12 28C + Si. Optical-model calculations that fit the forward angles

qua litativcly predict such behavior.

24 16 12 28c. Resonant Effects in the Mg( 0, C) Si Reaction

J. Cseh, I). F. Geesanan, W. IInning, D. G. Kovar, C. Olmer,M. Paul, S. J. Sanders, and J. P. Schiffer

Mesonaonce-like structures have been recently observed in

12 16the back-angle elastic and inelastic scattering of C and 0 on Si

(Refs. 1 and 2) and also in the back-angle excitation function of the24 16 12 28 3

Mg( 0, C) Si rea tion. Tho angular momenta at the resonance

energies are close to those of the grazing partial waves; this suggests the

possibility of observing resonance phenomena even at forward angles in

strongly surface-peaked direct reactions.

We have m08sured excitation functions at forward a-ngles

for the reaction 2 g(16 0,12 Si to the ground and first-ext ited states

of Si (lef. 4). Th c reaction p products were momc0 ntumn anal0y(z(d in the

Enge split-pole magn: tic spectrum ete r and detected in an ion i zation-chambe r

focal-plan detector. For neasuremcntts at and n00 r U" a gold lIol was

placed in front of the detector to stop the 160 beam.

1J. Ba rrette, M. J. LVine, I'. Braun-Mlunzinge r, G. M lBerkowitz,M. Gai, J. W. harris, and C. M. Jachcinski, Phys. Rtv. Ltt. 40, 445(1978).

2M. R. Clover, R. M. DeVries, R. Ost, N. J. A. Rust, R. N. Cherry,

Jr., and 11. E. Gove, Phys. Rev. Lett. 40, 1008 (1978).

3 P. Chevallier, D. Disdier, S. M. Lee, V. Rauch, G. Rudolf, and F.Scheibling, Proceedings of the International Confercncc on Nuclear Structure,Tokyo, September 5-10, 1977 (Organizing Committee, Tokyo, 1977), p. 654.

4 M. Paul, S. J. Sanders, J. Cseh, D. F. Geesaman, W. Henning,D. G. Kovar, C. Olmer, and J. P. Schiffer, Phys. Rev. Lett. 40, 1310(1978).

441

E ( 4Co) (Mev)

42 46 50 54

?* "Mg(LO, C) S (O)-

ob -J 4 24 M *g (10 1C 2S (

1 *"4 ,

1

38

57

4

3r

?r

IF

0 -

0. "

02

o.\ -

0 . 2022

'4

3 4-

28S (0

S B lo II

nE

Nb

V

. ? _ S((2+), 1.78 MeV

. " " lab

26 3C

Ec.m.(MC.

24Mg( 0, C)"Sl (0")

0 Elob 57 MeV

0.1

0.01

E 52 MeV

Ici

3;cos 8)

i, ECIL)48 MeV

001( n 25 3D. 35 o 4C0 45'

C.m.

Fig. 16. Excitation functions for the2 4Mg(16C, 1 2 V) 2 8 Si reaction.

Angular di stributions were ob-

tained at the energies indic t dby r row. . The solid lines -ireto guide th, .

Fig. 17. Angwli r di t ributi OIS

for the 24M (1 , 1 2 C) 2 Sj

reac ti on.

Figure 16 shows the excitation function for the r 'unA it

at 0 and for the ground and first-excited states near 11 (obtained by

measuring yields at three or four angles, between ( and 1-1, and inter-

polating the corresponding maximum cross section). PronoiUnced resonCn

structures are observed in the three excitation functions. Angular (istrib

tions are shown in Fig. 17 at the three resonance energies, E 28.2c'. m-.

31.2, and 34.2 MeV. The solid lines are the squares of Legendri.

2polynomials, PL (cos 0) with L = 21, 23, and 25, which have been fitted t

the data. The apparent simplicity of high angular momentum structures

high excitation implied by these measurements is not well understood.

1c e

bu-

,

t

It

III. 2c -45

* 4

4*

'I)

bN

III. 2c;3a

Although there is no clear r correlation between our forward-angle transfer

12 28measurements and the backward angle C + Si scattering data, the

periodicity and widths of the resonance-like structures are similar.

To resolve the origin of these resonance structures we are

presently engaged in a number of neasurements to extend the energy and24 16 12 28

angular r range of the Nlg( O, C) Si reaction and to measure backward-

16 24 hangle elastic scatter rinp, for the 0 + M-g channel.

3. STUDY OF QUASIILASTIC; DIRECT PROCESSES

Work at A rgonne has focused on some expe rim ents in which

the distribution of the total rea ctimi rtux is studied. The sum total of

quasielastic process s ,was found to be large enough so that channel coupling

must be important. In the past year the experiments on 40(;a and 8C

have been extended to higher energies (72 \1 eV) and the new data aret being

analyzed together with the older (56-k-V) data. [n addition , high-resolution experitrent was performed to get detailed infornittion on the most

important and strongest direct channels, those involving inelastic scattering.

a. eIncl;,stic h tt ring of 160 on lveni-Ca Isotopes

K. V. Rehn, W. Henning, J. R. irski.ne, and D. G. Kovar

We have completed the m easurcments of inelastic scatter tig

of i60 from the even-C. a isotopes at 56- and 60-M eV incident energy.

The data have been analyz,. d in terms of DW BA and courled-c channels

1 2calculations with codes PTOLEMY and CHUCK, respectively.

Particular emphasis was put on a detailed analysis of the

16 40 + - -O + Ca inelastic scattering where only a few states (2 , 3 , 5 ) are

populated at relatively low excitation energy thus permitting a rather

complete coupled-channels analysis. The results can be summarized as

1 D. H. Gloeckner, M. H. Macfarlane, and S. C. Pieper, Argonne

National Laboratory Topical Report ANL-76-11 (1976).2P. D. Kunz (unpublished); ORNL modified version.

46

III. 3a

follows: DWBA calculations based on distorted

waves that were fitted to elastic scattering fail

to reproduce the 3 and 5 inelastic angular

distributions (dashed lines, Fig. 18). Qoupled- --

channel calculations provide an adequate

description of the data (solid lines, Fig. 18).

The su'iess of the coupled-channel calculations

is mainly due to the modification of the elastic -

scattering distorted waves by thb explicit

coupling of other direct channels, prim ia rily th-

stro gll I excited 3~ state. This is in particular

(vidclnt for the excitation to the 5 state, whose

direct couplitig to the 3 state is negligible,.

This behavior is in con tradiction to the assump-

tion generally made in DW BA that in a direct-

reaction calculation for a given transition all

other nondi rc tl y -c oupld channels ca n be

trc-;ttU through a a verge absorptive potential.

Ihis seems of particular importace in view of

the failure of DWBa iin m ca ny h a vy-ion transfer 16 40I ig. 18. C + Ca

calcul; ti.,n s. Ih;it ad hoc changes in optical- inclas tic sca tte ri ng

model pa rameters can be used in many cases with (dashedliR s) and c oupledl

to reproduce transfer data with DWBA calcula - channels calculations

tions may find a natural explanation through the (solid lines).

behavior observed here.

DW BA and coupled channels calculations we re also per -

formed for the other Ca isotopes. Due to the large number of states in-

volved, the coupled channels calculations had to be restricted to straight-

forward calculations based on the parameters found for the 0 + 40Ca

system. In the average, these coupled-channel calculations were in better

agreement with data than were the DWBA predictions, in particular for

47

III. 3a,b

4? 'f 65,)42Ca( , Ca -

L E lab 60 MeV

" a - 0

1.8' V1eV -

L01 L-- L I .o1

C) 10 2 30* 46 50' 60 700 0

.cm.

44 , i 616 44

o 0, 3-E: ab60MeV

44Ca(o0)1.885 MeV

2 3e 4-L . 6 7

0" 200 30* 4Q0 500 6C0 700

Fig. 19. 0 inelastic scattering to the first citedd

0+ states in 4 2 (;a with coupled channel predictions.

the higher-multipolarity transitions. Thu couplud channels calculations

also provided a satisfactory description of the transition to the first

excited 0 states at 1.837 MeV and 1.885 MuV in 42Ca and 44Ca,respectively, through two-step processes via the first excited 2 states

(Fig. 19).

b. Energy Dependence of Quasielastic Processcs in 16+ 4 C48

Rea actions

D. G. Kovar, K. Daneshvar, M. Paul, D. F. Geesaman, W. Henning,K. K. Rehm, P. Sperr, S. L. Tabor, and S. E. Vigdor

To investigate the energy and target dependence of the reac-

tion mechanism of quasielastic processes in reactions induced by relatively

16 40 16 48"light" heavy ions, the 0 + Ca and 0 + Ca reactions have been

measured at 75 and 72 MeV, respectively. These measurements extend

the studies at 56 MeV (see Sec. III. 3a) to higher energies. The measure-

ments are of interest because (1) the energy range studied corresponds

to the region where the reaction mechanism apparently undergoes a dramatic

change (i. e. , the fusion strength "saturates" and the direct-rea ction strength

48

III. 3b, c

begins to grow rather strongly as the bombarding energy increases), and

(2) the rea action kinem-atics for the two targets favor different quasiela stic

channels, providing the opportunity to investigate the influence of the

various channels on the detailed properties of any specific channel.

Preliminary analyses reveal that while conventional IAWBA calculations do

predict some aspects of the observed behavior notablyv, the sadden increase

in strength for transfer reactions at energies P: 1b 65 NleV), the MW ;Al ab

predictions for the observed angular distributions poorly reproduce the

data. Since or m easu remtents include all direct-reaction channels of

significant s t renth , they should provide a stringent test of anV reaction

model which hopes to predict the details of r." action proc esses involved.

Effort in the )n ing ye a r will be spent in pe rfo rining coupled-c channel

calculations in the attempt to tindersta nd these processes.

c. \1 chaisin of Di1ret t k) .ctiorl Induced bV" on Ca

i. C. IKovar, W. IJenning, B. 7.eidman, Y. !is en, J. R . E rskine,II. T. Fu rtune, T. R. Ophel, iP. Sperr, and S. !-.. Vilgdor

16 48Analysis of eartier mneasirernents of the O+ Ca reaction

1 6at 1 ( O) 56 %1tV were < -pitted. The data consisted ', a ngular

labdistributions 1, ted with the final states opula t1 (1 in inllastic scatter-

16 15 16 17ing, single-nucleon transfer [( O, - N) and ( O, ()] , two-nulrcn

16 14 16 14 16 18transfer [ ( 0, C), ( O, N), and ( O, 0)], three-nucleon transfer

16 13 16 13 16 19 l10 lc:[( O, (), ( O B13), and ( O, O)], and ''exotic' transfer [( , N),

16 17 16 15( O, N), and ( O, C)] reactions. Effort wa s spent this ya r in con -

paring DWBA calculations with the observed resodlts. Ihi comparison of

theory and data indicated that in a majority of the trans itiops rect tion

processes more -ornplex than the one-step process a re involved. 'a lcil-

lations using coupled-channel models are planned in the next year for this

associated data in the attempt to understand the reaction mechanisms

involved.

1 D. G. Kovar et al. , Phys. Rev. C 17, 83 (1978).

49

III. 3d;4a

d.Th 16Q 12 i8 14d. The ( 1, C) ;Ind ( O, 1: Reactions and the Quasielastic Cross

Section As a Function of Mass Number

W. henning, .. Ka rrctt, * P. J). Bond, ind .\. IeVine:

In 1$I he C) and C) induc td totat li re ct -transfer cross sections

we re measured for a number of tarts at omp0 a able kinematic conditions,

i e. , rough\ the same relative energy above the Coulomb barrier.

Pa rticular interest was focused on the relative cross section for the

1t, 12 18 11( 0, C) and ( ,1- C:) reactions to study wh ethter correlated transfer

of nucleons (pairs, 'u" transfer) can be observed. [he data are in the

process of being analyzed now. Ihe first results indicatV thait, super-

imposed over the kinematic effects, there a re structure effects present.

"l. I-:AVY -lON-INDUCEI) FISSION AND QUASIFISSION

This is an important are;i of heavy-ion-induced reactions to

be pursued with the new suipronducting linac. Since such studies requirehigher energies than we availabb- it A rg onne, staff mernbe rs have

collaborated with others, at the GSI in I);i rmstaldt Germany, and atB rookha ven in these expe rim cents.

a. H(;ivy -Ion -Induced Fissicn at Hligh An(,uln r M1oment a

W. I Ienning, O. Kis tn e r,* NI. IcVine, and A. Schwa rz schild*

Th c possibility of studying the behavior (f nuclei at yery

high angular momentum is one of the exciting aspects of heavy -ion-induced

reactions. We have measured first-chance fission -vents in the mass

ra g A-gc 'N 185 induc ed by ver y ei v ions f rom th c Brookhatv"'n double -

tandem facility. Ta rgets of tellurium and tin were bombarded with -250-

NM(V ~ Fe ions and the fission-yield excitation function was studied near

threshold. From general considerations one expects fission at these

energies from only high angular monnturn states; such an experiment

Brookhaven National Laboratory, Upton, New York.

50

III. 4a -c

thus gives a unique opportunity to obtain inf, rm-a ton ibiut mn moments of

inertia and fission barriers at high angular m1n wnr1 lt in', (quintitics of great

theoretical interest. The first results are being analyzed; future measure-

ments are pl;cnned involving the study of fission-barrier behavior as a

function of neutron t xc ss, by bombarding, for example, targets from

112 12. 58 64Sn tii -n with betms from Ni to Ni.

b. Quasifission Reactions Induced by 236-MeV Ar on Ca, Fi, r Iii,and Ni Ta rgets

B. ZeidTmnan, J. Barr tte,: P. 13rdun -Munzing r,* C. K. Gelbk,f1. I,. larin y , K. 1). Ilildenbrand,t U. Lynen, t and 11. F. W iL tr

Va rious targets in the If2p shell were bombarded with

23( - 1eV 10Ar inns from the UNILAC actelAerator at Darnstadt in order

to st ldv ma ss ;tnd (hi rgec distributions fr<vi fissiion -like reactions. Thc

data have bean analyzed in terms of poiential-.ntrgy surfaces which

dscribc the' initial i (listributi on of binary products convoluted with am

elaborate prograim that calculates the decays of the highly excited nuclei.

This sii mpli proiedurc, although complicActed in detail, fields good arc'-

ment with the distributions in i !s and charge obscrv( . I he proc edur

su gg( sts the feaisibhilit of estim ;tti nig and iptim z17 ing yie Ilds of nuclei fair

from stabhilit v by proper r hoice of target and projec tile enrg. his pr jctis compl t(d; and i pale r s have been submitt ed for publi, ation.

32 ~'c. Fission C ha racteristics of thr C;omposite System S + Ti

B. Zeidran, J. Pai rretti',* P. Br;aun -Mnnzin r,* A. Ganp, . .

Cclbkt a I. 1,, Ili rnev, Ih. Walcher, Ind i1. 1:. We'n. r

32 (The fission characteristics of the systim S + ii e re

studied between K(325) 121 and 166 Me V at the Hcidelberi M I dhm.

The evolution of mass and angular distributions indicates that variation of

MPI, Heidelberg, Germany.t

GSI, Darmstadt, Germany.

III. 4c;5

energy at energies such as will be available from the ANL superconducting

linac is required to elucidate the various trends. 1'his project is completed

and papers describing the research have been published in Phys. Rev. Lett.

36, 849 (1976); Nucl. Phys. A269, 460 (1976); and Nucl. Phys. A279, 125

(1977).

5. HIGiI ANGU LAR MOM N1IUM STA'l ES IN NUCLI

One of the most exciting frontn- rs in nucle;tr physics involves

the investigation of nuclei at very high angal;tr momenta. 'he present

facilities at A rgonne t re not best suited for such studies, but the supe r-

conlducting-lin;o booster will accelerate hea vier plirticlts to the energies

where such studio s will become very practiAI. In preparation for this,Argonne staff m members have been working At fa cilities in Denima rk, Gerum ny,and at Chalk River during the past yea r. ()ii( of the most signific ant

developments in nuclear r physics in 1977 was the discovery by ; Niels Bohr

Institute -GSI-Argonne collaboration of a cluster of high-spin isomers.

'l'hest isomers ;t re possible( yra st traps which may provide both a sigIature

of dramatic nuclear-shape change as function of spin ;tnd aso a means to

study nuclear structure to much higher spils than has previously been

possible. 1"low-up spectrOscopi, studies of the initial suirvv perform'tdat GSI have begun with Argoni c colIab1)') ration at Cha lk River ancd at the

Niels Bohr Instittit(.

1 oMi ore cunven tioinaI studies, using t!( ( 0,xn) red ction nod

Coulom b excitti fn, ;ire being < untinu1ed to investigate the effet s olneutron-shell and sub-shell closiires near N 8 82 and 0-4. Son- sear( hes

for high-energy x ra ys from the composite systems C -+ Sn ;nd Cu + B-i

(Z 91 ;tnd 112) have also been carrion( out.

52

III. ';, b

a. Search for High Spin Isomrs

J. Pcd'c rs en, B. i. Ba ck, t F. MI. Bernthal, S. Bjlrnholm,J. Borggre(n,; O. Christ tnstn,1 F. Folkmann B. iet rshkind

T. L. Khuo , \. N rim an, F. lfhlhofer, a rnd G. SIt tt 11:

An - xtunsive sea rch for delayed y radiation of half-lives

longer than 10 ns and high multiplicity was performed by producing

more than one hundred compound nuclei between Ba and Pb in bombard-

Mcnts with Ar, '1 i, rnd 65Cu beams .it GSI, Germiny. I went diffe 1-

ent compound s, stens gavt( t a r (videnc( of high spin is n:Wrism with

multiplicities between 8 and 18. Therc is a clustering (1 tiKse isomers

In unt region of the periodic tabl< with 64 - 71 and S2 N 88; no

isomers were observed outside this region. I hus, it apeirs that fluclei

which a r(e dcfo rn(d aind p rohlt t in th ground state (10 not give rise to yrast

trap-). This may indict t that no dranwiti change in shape from prd:Ite to

obl;te oc curs s spin 1i(i c(a"s . ()n the (the r had111, tht' p ssibi lit\ < a

sphtri< ;tl tec oblate t ransiti n in those cases where high spill isotlers exist

will bt pr()bed in continuing studies 8imed; at determining the energies and

SpIns of the isomers. Th, main result., (A the work hLI been publili sh-d

F Ih s. Re . I (tt . ', m (1' 7)a .

b. Iigh-Spin Structure Of Gd and l(rvclopmnent Of an I nr; -

Spect rum te r

T. I. 1.hou, F. NI. Burnth;al,: T. Borggrcn, B. i Icrshkind,

J. Pedersc n, and G. Slutten*

The search for high-spin isumn rs 't GI ( bove r( port)

indicated that Gd is a good candidate fur the. (, ;r rt 1, ci t rst res.

Gamma-ray studies weure conducted at the Nitls Bubhr institute , 1e)(nia rk

1341 16, 13 16using the Ba( 0, 3n) and 13a( i0,4n) reactions to idcntifv the 1 Ve 1

Niels Bohr Institute, Copenhagen, Denmark.

tChemistry Division, ANL.

GSI, Darmstadt, Germany.

III. 5b,c

structure of 147Gd to moderately high spin. In conjunction with the GSI

data, several isomers were identified at 998 keV - 13/2 , 2760 keV - 21/2 ,

3582 key - 27/2 and 6517 keV - (19/2?). The last isomer was strongly

40 50populated in Ar and 5 Ti bombrardment at GSI but only very weakly

populated in 160 irradiation. In order to accentuate the weak tranlsitionus

de-excitinti it, a sum -energy spectroneter'r was op rat d in coincid n e

with the Ge(Li) detector.

Ihe sum spectrometer consisted of a H in. 10 in. Nal

crystal divided into two sections. The sum signal was used to s -p(,rat,

different xn re action channels and a triple < oincidenc(e involving the Ge (Li)

and the two Na sectors acted as a multiplicity filter. Dvelopmvi (ntcil work

was also done on using such a sum spectrorm (t4r for observing evapor nation

residues which have recoiled out of a shielded ta rget. Such ar a rra ngemert

c anii be used for measuring thc" excitation en--rgies of isomers and for

detailed spectroscopic studies of isomers.

c. Study of Iigh Spin Isomeric Statc Near the (7los ed Neutron Sh II,N - 82

T. L. Khoo, 1. K. Smlither, ,. Andrews , B. 1Iaa s,a ). HIausstr,'

D. l orn, and 1). Wa rd

Pr eviou s exie rim nts performed in col[aboration with the

Niels Bohr Institute ad GSI groups have indicated a group of hi glh-spin

ison-ers with 64 Z ' 71 and 82 N - 88. llowever, the origin (isotopic

parentage), energies and spins of these isomers were not determined in

this investigation. To help alleVi ate this situation, we have studied isomers

in TPb, IDy, and Er isotopes formed by bombarding 12,122,124 d

122, 124 32' e targets with S beams. The xpe rim nits were performed at

the Chalk River Tandem Laboratory. A multiplicity filter consisting of four

large Nal detectors was used in coincidence with a large Ge(Li) y detector

to help select high-spin delayed events. Timing between the pulsed beam

Chalk River Nuclear Laboratories, Chalk River, Ontario, Canada.

54

III. 5c

TABL- 1. Isomers observed inTFe targets.

Compound \lultipli< Ity Multipli it\

32s ,stem GSI with S

1 12 t 2 9

1 5.1

152

156I-. r

1 54

13 t 2

15

15 2

18 2

12

1;

1 (

5ti

11 3

I .4

4

5

-1

12-13

-13

3 2S-induced reactions with Sn and

I.i sotm er

152-). 1 r" i , 17

11;'f.. 1 ) , 20, )17. t 1Dy 26, 27

10. 1 I 30,31

I.9 I)\ 39/2

t.* (1 15/2

6.6Gd (-49/2)

12. D

(7 1) -

1*18-1. 1 1) 1 1

1.T(U. 6 11)

. 18

-) ~ 148 3

2.8 I-r153

6.5 I r

2. r (1 5 Ho)

(. 3 ( 15 1 )

and a Ge(Li) detector, y-y coincidence, x-ray -y coiniden v (for 7 identifi-

cation), directional correlation and excitation function ma SrtimnntS \wt re

performed. A rapid search for delayed a's with high ', mltiplicit \ was

also conducted with negative results.

Isomeric states have been observed in each of the , ompound

systems formed; the isotopic origins of most of the isomers have also been

determined. Table I summarizes the results on isomeric states.

Isone'ri,isumcr

systt m

55

111. 5c

10 15 20

Or

5-

60ns*

0 -0

I (h)25 30 35-I---

4 n

4'' s

5001(I+1) [

-70ps *

-g=4MeV

25C f 21 =120 MeV -

s h2 SPHERE

-

=150

MeV

2 OBLATE

1000 1500h21

We have also

begun detailed spectroscopic

studies oni 1 5 1 , 1 5 2 Dy. Cas-

caries of 10-11 coincident

's hve been observed by

del;t, '- e -(in( idenee techniques

to feed the 6-MeV isomers in

both c cases. T1'he spins of the

highest -lying states arc

let ntatively 67/2 end 37 in

he respective C;,se5, much

higher than has ever prey:"~ -

lv been obserVed in any

nuclIto .

Fig. 20. Plot of excitation ene rgy vs A plot oif vs

1(I + 1) for v rast line of 1 (iDy.1(1 + 1) f r thit- rast sLtat, o;:f

1 521 )\ i" shlOwn in Fig. 20.

The striking feature is tha;it for I 14, on the average, 11 E + F 2/LD) I(I+ 1).

Such a b)ehavior is indeed expected fur a Fe rni gas and the data

proba bl provide the first experimental demonstration of this feature.

Furthermore, 24/- 1-10 %leV , a value a roger than thmt for a rigid

sphere by 20', but ( consistent with that expected for a rigid oblat, spheroid

with @ 3 0.3. It is tempting to suggest thait the slop( of the yra st line

suggests a large obla te d formation. Hiowe ver, shell ffec 'ts ca in rease

the effective moment of inertia and the observed large value is probably%

due to a combination of shell structure and deformation. At any rate, the

statement can be made that the irregular rity of the %-ra st lint suggests that

1 5 2 Dy does not become prolate even at the very high spins observed. A

prolate shape would have given rise to a smooth yrast line generated plainly

by collective rotation.

5C

III. 5c, d

The remarkably large populations of the 6-MeV isumers in151 152 124 32_

Dy and Dy [~70% of the respective Sn ( S, xn) reactions]

are also consistent with this conclusion. With a spherical or obl , -.hapc

one expects a rapid funneling of the y decay to the yrast lint via -t -titical

cascades following neutron emission. With a prolate or triaxial sha p),

enhanced st rctchcd 2 t ransitions can compete with the statistical tran sit on

several M eV above the yrast line t he 'y ideca y is thus channeled along

paths pa; railel tc th, yr;cst lint but several MNItV above it, with the c on-

sequence that the yrast lint itself is largely bypassed at Lt rge spin. This

may provide an explanation for why spins no higher thatn, typically, 22 -.

have been obscrv'd in previous (11. I., \n) studcieS which have mainly been

< nt re d tin prolait c ;s s.

d. Pd(16

R. K. Snither, \. . I riedtimin, I. Ahimid, 11d 1). l.. I3cshnellt

102, 10 1, l1 , 1o 1) 8 16, 118, 12t) 1i2reatiOnsI }1t ' ' ' ~li( c_, Xn1) - e c i n

wetre used to study the level struttare 4 thu neutron deficient Xe isotopes.

[he ncin obje tive' was to observe in Ku the la rge nuclear--t ruturu chant

that occ urs in Cd and Te :1 tht neutron numube r N - 60-t. (>t F'i. 21

for a conpa ri son ol the ground - state hands in Xe and Cd.) Ihis nuclet r -

st rn ture change (a S Ide n dccr tase in tht level spacings in the ground-

state rotation I band with inc rea sing itut r en nun b( r) is seei in these

expe rim uints in tht level sche mes of 11O (N 6 1) \ (N hi) , 11d

120Xe (N - 66). The nuclear structure change appeo rs iinaffet ti d by the

closing of the proton shell at Z = 50. It appa rs to be a sst ) ii tid with the

closure of a ne utron subsh eli at N = 62-6-1. V uturc experiments (1 8)1t i 11 1

will continue to investigate this structure c ha nge in \c tnd }e and

other nearby nuclei (1 16, 118, 120Ba).

Chemistry Division, ANL.

tNorthern Illinois Unive rsity, DeKalb, Illinois.

III. 5d, e

-8' Cd (,'=48)

(a)

44Wir

C)

STRUCTURECHlANGE

L J - - - - - - - - - - - - - - -N 50 52 54 5E 5H 60 62 64 66 68 70 72 74 76 78 AO P,At 98 100 102 104 106 108 110 12 114 115 118 120 122 124 126 128 3(,

3s-

xe(7=54)

I

IC)

to.

-10'I

(b) '

_.

- '

Fig. 21. level structure

3-

z+0

-J

4' -

N= SC . '.4 56 ,H 60 62 64 66 68 7U 7? 74 '6 7H W, H:'A: 104 106 08 110 112 114 116 118 120 122 124 126 128 130 132 154 1 56

1-48, 150, I5,1.e. I I-, vy -lon Coulomb Excit.Ition in , , , 5

R. K. Smithcr, 1). 1. Bushnell,: A. M. Fritedman,t and I. A hm(1a:t

The object. of this work is to improve the accuracy of the

relative B(I -2) values for the low-lying transitions in the even-i, even-N

Sm nuclei and in the case of148

Sml to measurt- sone oi the B( (.2) values

thaIt haive not been measured in previous experiments because of their

extremely low cross sections. The improvement in accuracy is needed

to make meaningful comparisons with theory. Often the different phonon

Northern Illinois University, DeKalb, Illinois.

tChemistry Division, ANL.

of the ground-state bandsin tht Cd (.c) and Xe (b)isotopes as seen in the

(111, xn) rcia actions. The

st ru( tore change is

evidt-nt in the Cd levelsbet ween N = 60 andN (>6. A similar

change :, ppcars to be

present in the Xe nu< Liin a simiI; r region.

W

W

"a

58

- - - -6*

-4'

1)

III. 5e

200C}

'T

Y IWJ-

-J

'.

TJr

'

.

*1

L___1

I

Fig. 22. Partial l'vel schcnm :f Sm with gamma

transitions observed following C inb t ttiOn

with a 160 heavy-ion beam.

or rotor models differ in their predictions of branching ratios, et(. by a

factor of only 2 or 3; thus experinients with 50( rr(rs a rc nut much help

in comparing models. Of special interest inl 14 nv wa the r"s0luitiOn Of

four closely-spaced levels at 1425.9 keV, 0 ; 1454.7 keV, 2 ; 14,1. 1 keV,

1~; 1465.7 k.V, (1 , 2 , 3 ). (See Fig. 22.) I'he list thr-e ~1"re often

unresolved and confused in previous experiments. Yhe identification and

resolution of the 0+ state at 1165. 4 keV is also important. In previous

experiments its :xcitation was often hidden under tht strung excitation of

the 3 state at 1161.9 keV. A preliminary report of this work app eIrs in

the Proceedings of the Tokyo Nuclear Structure Conference (September ;-10,

1977).

I

59

III. 5f;6

f. Heavy-Ion oppositee X Rays

R. K. Smither, NV. Henning, A. M. Friedman,* I. Ahmad,1 and

D. L. BushnellI

When heavy ions are moment ril- close together, it is

possible for them to emit x rays with energies similar to what would be

emitted by an atom with Z = Z+ 7 , the sum of the Z's of the projectile;) t

and the target. A new target chamber with provisions for an annular

surface barrier detector to detect back-scattered ions and also to bury

the beam a long way from the target was built for this experime It. Pre-

liminary d.tta were taken for the Cu + Sm and Cu + Bi systems. 1 y

requiring a coincilefnce between the composite x ray and the backscattered

ion, it is possible to convctrt the resulting continuum of x-ray energies

into a relatively harp peak. This makes their presence much easier to

discern. A trace of the comnposite x ray is suggested in th- Cu + Bi data

but tlit experiment suffer red from low count r;it ' beLtusb of low heavy -ion

beam currents. l'hese experiments will be repeated with the upgraded

tandem and its more intense heavy-ion b< ams.

Chemistry Division, ANL.

Northe rn Illinois Unive rsity, De K lb, Illinois.

6. NEW BVAM LINE FOR THE SUPERCONDUCTING LINAC; BOOSTER

With the heavy -ion beam from the superconducting-linac

energy booster, new classes of exneriments will uecomfle possible. Beams

with heavier projectiles and higher energies will be provided, with specialernphtsis placed on the quality of the beaimis, in spacial, energy, and timeresolution. To begin research with these beams, new beam lines and new

experimental flciliti es are required. In order to optimize use of very

limited equipment and operating funds, severe compromises had to be

made. The initial beam line will be at 00, with respect to the linac, with

no charge-state separation or rebunching. The beam will be stripped before

entering the 900 analyzing magnet of the tandem.

60

III . >a

The layout of the beam line was made after careful study ofthe beam optics so that four experimental stations will be accommodated

on a singl< lint. Focusing and diagnostic elem -nts had to be designed to

permit the use of these four stations. With many expe riments using heavy

ions, the quality of the vacuum obtained in the beam liies and the expe ri -

mental scattering chambers can place serious limits on the kin d. of

expe rim ents that can be tarrited out as well as on their quality. It was

decided to keep the vacuum system as clean as possible and to attempt to

eliminate organic components; the system was designed accordingly.

Thct major expt rimen tal station will be ;t new >5-in. st .tter-

ing chamber; this was determined to be me r cost -fftctivn thin the

refurbishing of an existing >00-in. champ ber. A nrtuitremn/chaerged-pa rtitclt,

time--f-flight system will be const rtctcd by the ( hemistr I Division.

One station will incorporate a g*amma -ray-nmiultiplicity systt m, and another

will make use uf an existing rabbit and lie jet, for del . el radiations.

a. Zero Degree Beam I ine v r New jxperimentml Art ;1. G. kova r, W. 1 .. vans, W. I Ibnling, :aien B. Zeidmian

The 0 bcam line for the new experimential ;iret ( ftr the

super rconducting linuic) was designed and the i ndividutel ( )1m)nonents are in

the process of being piircthased and fabri t( ; ,t t i - V - .

line will accolnuodte ill experimnl tati ns e or n .j I K . si.: I

experimncits with th. linV . A spec iacl effort was thert'fcere mmdt' to design

;ta vout whti h makes optimum use of tht beam proPerties and physical

p .~ e 1Fu r (' ptrimc ntml stations, listed in sequence from the Ii ,

o sE 0SCALE Cele

E

x~~ IO'--I

S20 ' -

E 65 SCATT NEUTRON TOF v>.20 CHAMBER SCATT CHAMBER CHAMHP

-x - - - x- - --- CT VAT 0Nt ISATIAON

Fig. 23. Target a rea: Phase I (zero derc-' )eaI.m line).

tI

Ill. a -c

are planned: (1) a general purpose 65-in. scattering chamber, (2) a

charged-pa rticle/neutron time-of-flight chamber, (3) a y-multiplicity

chamber, and (4) an activation chamber. As can be seen in Fig. 23, the

magnetic elements on the beam line include a quadrupoli triplet , two

quadrupole doublets, and two pairs of x-y steerers. The beam line is

expected to be installed in 1978.

b. Ta rget St tion for delayed Activities ('n the Superconducting Linac

(. N. I)avids

A t.argct station to be u se(l for the study of nuclei far from

st.--bility is pl;.nned on the Oo beim line of the step, rconducting lin.ac . It

will have ;a pumping station nd an in-line cold trap fur vacuum isolation.

' rgct chambers ;l ready in existence will be t One tt(d. These are:

(1) a mlt iplt -ta rget rabbit system for P-y sp(ect ros( opy studio (s of delayed

ativities with half-lives lomng.r th ri 1 44< und, (2) a helitum- et recoil

transfer system for [i, y ;ad -ele t d pa rticlc studies on nuclides with

half-lives lon12r than I second, a1( ( ,) an in-beam chamber 1or V, y ;ind( -

delayed partit I, e-asuremnnts on nuclides with half-lives less th;w 1

second. :\ mechanical beam chopper ard beam shutter will be required

for these experi ment s.

C Beam ptiis fur the Zero ID) eLgret I'ea m Line

B. /eidman and I). G. Kovar

The benm transport system for the zer u-cegree beam lint

was designed al1nd specified with the use of t he pr(-ram TIRANSPOR I . l'he

system utilizes one quadrupole triplitt anitd two quad rupole doublets to

provide four stations for e xpirimental studies. Ttihe triplet, the first

(lirment after the linac, not only provides a waist at the entere r of the

65-in. seatte ring chamber and maintains beam quality for the elements

downstream, but also serves as the primary focusing element for future

111.6( -4

development of other beam lines. The first doublet services the neutron-

time-of-flight station, while the downstream doublet provides well focused

beams for both ti gamma-ray facility and the activation station. Ihe

system minimizes path-length differences so that the time structure of the

beam is preserved. At all stations, the beam spot is epproximn it 1. 2 mm

diarneter or less. Design of additional beam lines is Itnderwa';.

d. Beam Diagnostics in the New Ta rget A rea

W. lenninzig and 1). (. !Kovar

A simple beam diagziostic syst en, - signed for the n

beam line in the new ta rgct r,. It 1 design I nize present cOs t

with provision for easy expansion if future ,e ds .rise. At three locations

serving the four expe r-mental setups, mmltiport beam-diagnostics box -s

will be inlstallt-d, equipped with a Faraday cup and a c,)llim.atorir/quartz

insert, both moui ted (,,l me'til-bellows sealed, r< , . a~ir'- tivited

feedthruughIs. I he diaeuiosti. boxes allow for I r- of profile

monitoring de .ces ;,nd movable slits.

'a uum Systen in New Target Arc:,

i 'e: ing, 1). G. hova r, ;nd .J. >. orth-itgton

The vacuum syst tmn in the new target a rea was designed,

aiming ;tt (1) a hidroc a rbon-free vae. ium to prevent carbon buildup on

ta gets, (2) low pressure to reduce ha r < xcha ng for the he Iviest ions,

and (3) general good high-vacuumi chricteristics to minimize accidental

contamination of the superconducting lina c. .\11-minetal components a re

used wherever possible. Magnetic ion pumps a re used for the beam -line

sections based on minimum ost considerations and on the fact that Inmping

speed plays a minor role due to the limiting beam-in-line condu ctnce. At the

experimental setups cryogenic pumping is used wherever r pus sihl .

111. 6f, g

f. 65-in. Scattering Chamber in Ncw I irget Arca

W. Henning, D. G. Kovar, and J. N. Worthington

A new general-purpose scattering chamber is being designed

and constructed for experiments with beams from the superconducting linac.

During the first stage of operation of the linac it will be located diretly

after the accelerator to make immediate use of the narrow time structure

of the beam pulses. Later it will be moved to a separate beam line, after

the rebuncher and the charge selection m agnet are installed.

Special emphasis is put on a light-weight, low-cost structure

by requiring minimum accxura( y for the chamber body end establishing the

required experim, it I accuracy with respI t t to an into rior floating base

plate. The " 0-in. diameter of the cha mber allows for high angula r accuracy

mnd sufficient space for time-of-flight mea surements. Its height (if 36 in.

provides the capability for out-of-plane motion of detectors. l )ur

independent arms allow 3000 amgule r rotati ae nd rvdial motion. The

chamber vacuum will be hvdrot arhon - free t~ prevent ca rbon buiIdup on the

targets and to comply with the vacuum requirements of the linac system.

The design of the chamber body and the interior structure is completed andl

now under construction.

g. y -1 v facilityy for the Ncw 3 'eamn Line

I . L. Khon, R. K. Snither, and I. Ahmad*

A general purpose y- ray fa cility has been desi giee d which

allows angula r distribution and coincident e measu rements. Siev ra l

different types of ctinc idcence c(xperim *nts are possible: G ( Li)-Gt (Li),

Ge(Li)-sum/niltiplicity spectromreter, and lait r Ge(Li)-,a rtic le detector

and particle-d t 'cto r-scam /multiplicity spec tr meter. T he sum/niult i plicity

spectr)ometer consists of two 6 in. ,r 13 in. NaI dt tcectors, each divided

into two segments. The total y-ray energy in a rta ction as well as the

Chemistry Division, ANL.

64

I11. 6 g;7a

y multiplicity can be simultaneously measured with this device. A 3-

position, rotatable target ladder will be incorporated. There will be

provisions for either stopping the beam at the target (.allowine 0 measure-

ments) or at a Faraday cup ~2 m downstream.

7. EQUIPMENT DEIVELOPMEI 1

Most of the efforts in Heavy-lon Physics on equipment develto>-

n ('t and other supporting activities have been devoted to the implementatiand use of -h superronduc ting-linac booster and tt the associated new

beam lin,. [ he two activities reported here represent a major effort onimprovinga h av "-1on fuc al-plain dttect tors for magnetic spectrographs.The Argonne design of such a detector is a pionet ring one and is copiedworldwide. T he target production effort is also rtp)rtecl herein.

I leavy-Iv -I 1- ocal Pflan( Detectors for the M"gn"ti> 'rr

J. !. . rskint and J. (. -oltzfus

The second ionization-type focal-plani detector has been

completed anid tested. Its performance is essentially the same as the

original detector, except that t he new counter is ne rly twice as deep,

which oives it -nich larger dynamic r n1 . he m i mor virtue of the new

counter is that there is now space available inside thte gas containing box to

add features which will considerably improve its performance <.

The first major change is to use a better method of readout

for the two position measurtrnents. In the original detector the rist-time

difft rence method of Borkowski is us td. Ihe int rin sic simlit it of this

method is offset by several l problems: the relatively slow rLUaiout ti ',

the nonlinearity of the position c ;alibration, and the cha nges in tht cAlibra -

tion due to alt red electrical conditions. The new readout techni qut will

use the lumped ,onstant delay line used very successfully\ u groups :t

Michigan State Ulniversit\ and Brookhaven. Cathode, pit kup strips \w ill

surround the anode wire of the proportional counter. Thtse pi kun strips

t, , Ill. 7a, b

(spaced 0. 1 in.) are cornected to the delay line. I'he propagation time

along the new delay line is about 5 times faster than what is now used.

The stability and linearity of the position calibration is a major improvement

and results from the fact that the time delay constants arc rigidly built

into the external deli y line. Ihis improved stabilit% will make it much

easier to use the angular measurement generated frorn the differences

bt tween the two position signals in the detector.

In order to predict the performance of the present counters

or speculative variations of it, a compute r code was written to calculate the

position and tnt-rgy resolution due to v riou s physical effects, principally

energy-loss straggling and multipl< sc;tt- With this code the per-

formance of this second itnizatitoni-tvri dt i tar for "100-MI eV nickel ions

was calculated, for both normal and 4o incident Ihese results show

that 1.5 mnm position resolution should be obtain( ( -t 45 incidence com-

pa red to 1 . 2 mim resolution for normal incidence. % hile there are some

questions rega riding the a ccuracv of these calculations, it app,) r"s c ri.

that the improve ment in resolution from normal incidence on the detit t r

is not as la rgo as was previously expected. This then t)rings into question

thct necessity of redesigning nd rebuilding the ma gneti c spectrogra ph so

as to achieve normal incidence on the detector.

b. Nuclear Tt rt t Makin.; nd Development

G. E. Thomas

The Physics Division has a f;j ility which produc-es very thin

targets, tspti i1l1\ for experime: i at the Tand, i and I)vrnamitren ",t eler-

ators, and in ;tdditinIi, for the other members of the Division as well as

for (xperim centers from other divisions of the Laborato ry.

Over 900 t; rgets wepr prpa red during the last year, again

varying in thickness front a small fra ctional mnolt r in thickn css to

-1.5 mg / n . The different dlennts, isotopes, ,r corniotunds evaporated

or rolled included Al, Au, Ag, 10,11 209 12 13 40,42,48r,, B, Bi, C, Ca, Cu,

Ill. 7 b

5 1, i , LiF, '4, 2 ' 26Mg, N, i, 8 Ni, NiO, Nb, 1d,, 1(W,

Pt, Fi, WO 3, Au + Si, And Al2 3.

Self -supporting ta rgets requi ring p. rti( ala r skills which

40,42,48 101 106 108 2 4 , 2 5, 2 6 Mwere made included ' (it, U i, ' ' I 'd, Ind -9 g.

Many sandwich targets were produc< <1, 'me of tht most

elaborate being layers of Au + Ni + Au + Ni + Au ont: . stainless steel

backing. Another had two different ta rgets on the saimt friaa. . I mv rs

>f nickel and gold were 4vapor;mtt-d onto the en(L of small mrmmnialn

r -t ;Ils for use Is thrmocouples. A composite simple d a rbon foils

produced a ta r get 1400 microgram th i<.

We have done work, P, Kdtha td.., TLAt: r t.

)ivi s.on, for the (henical Ingineering Division, th e (hemistrv Division,

th' .\1trias S ience 1)i visinfl th( Solar Group, the Applied Physic's

Division, and the University of (-hiram .

IV

IV. CHARGLD-PARTICLE RLEEARLH

INTRODUCE LION

The cha rged -particl r search program employs light ions(A K 4) at both accelerators within the P'hvsics Division. The program

uses 30% of the bem;)rn time at the Dynarn itron and at the Tandem. The

research is broadly based, ranging front careful studies of low-energy

exothermic light-ion reactions, which could st rvt' as future energy

sources, to studi 's on the fundamental -aspf'cts of the weak interaction

as evidence(d in nuclear p roc(ss (s. Important and systeratic studies in

nuclear structure are also carried out in the 2 p-If shell. A new venture

in medium- mass nuclei focuses on nuclear structure- and reactions of

astrophysical significance. High-resolution la rg(--volum(i NaI spec-

trornetrs have becun developed t(:) inve stigate giant r'sona nces via radiative

capture of protons and a I particles.

69

IV. Aa

A. CIIAHG1-.D-PA TI(.Lf. R ES-ARCIJ ATl 1111. DYNAMI PUN

This prcigrai consi ts of two print ir;I rese;t r h thrusts.

'he" 1;trg-st program in te rms of AtN14 imianpov.,tr i5 the ouigoing invEtsti-

g.tiOfa into (.xothermicI rea< tions with light nu( I. .I 1t re&a tions to be

sttrdl-d a re selit ted (dn the bas of their irit ri interest to nuclear

p)hysi( s, istrtiphysics, and thlii r pcotenrti;al use as .t < lean fuel ain controlle-d

thermonr tu, Ite;; r resea r( h .,ppli( ations.

TI. )t (,r program ff is a continuatiofn (t the rt( ently initiated

rose;( r( h into studi(Es of the findarnental aspectt of weak intcractinS as

observed in nuc le. IDati are tjEifg t.:ken on the ~i - ngul~ar ( Errelations

in A 8 as a f , tiir l euid-point energy. "I his will dll)V.w a very det;ili'd

test of CVC ;tnd le ensitivt to th( 'Xist'in I xi -VeI v ur s( t( r >-d-< l( s

inter;t ti<>ns. I his expfe rimunet will lbe < Of nwh t *Vd by the end of 1'+7 r>. A

(li;llenging experimt en'ftI to mrle;lsure thE parity , imIxirig ( ;eused( bi, thii tietitral

weak (urr ti t is flow bcifiL! ;, seri l (I <t ()ll iburati'n ! ith; a r Se t r( Ier

from St;rifurtd University).

(> 7 (> 7 (>

_._ _ i(11d p) '1 L. Li(d n) } ; ,--:nd I.i_((1, N) ucl 4;tr 1'.(_e ti ns at Low

A. J. Llwyrn, 1. I.. i<, fah in, P. 1". Ilullanfd, C. IN. D;vids,I. M.1 -t [r- it zm 'i stIr, tad F. i . M o ring

I Ie ;i bsolut diff( r] f r t if I and total r(". tin ( russ se tltns

for the luw-('nergy inteructiOn (l (attrons with Li pruVide the dcata base

n(('e Ss;4r1 for the (V;i l tBti Ol O1 th' t sib ii < I :ll i i ;s (1("1 fII m nt

in th1 fututrt (I Vel(.1)plm( nt (I 4bi t r 114(-( therninln i t;, 1 (Ir Vi -( . :\in I lyses

(f e1pri nents designed t s tt1 nI th ret'l(vV;nt ross se< tiuins at 4fntrgi(s

between . 1 a nd 1 i tV to a pr iiOnE of a but 10'r, JH rtc rrn over the

last fv: \'( rs, have betr c(rfpl't(, aia( p ipcr ((tBriling the pIrO, (dur(s

and r(tsults has been recently publish(-d. 1 As an ex; ml)It of s( 1e of our

results, the total (a ngle-integr;ite(d) reafctfl(P cross section for the

6Li(d, ()(n reaction at (no rgie s betwt en 0. 1 and 1 Ne V is shown in Fig. 24

compared to previous measurements.

'A. J. Elwyn, R. E. Holland, C. N. i)avids, L. Mc yer-Schutzmeister,J. E. Monahan, F. P. Mooring, and W. Ray, Jr., Phys. Rev. C 16, 1744(1977).

70

64

60 c

" i

I'-

l-i. -. at;El (II glc -integr .t("d) rearc-

tion c ross sec tions in the G V-(d, i)r

re~acti on as a function of deut cronen e rg\ . l he rel;tivye precisiOn of

the present results is indi< wt d by the(r ror ba rs. The previous results

ar e b si'cl on ptibli shed pre - 1 972

reports (set'. R(f. 1). The dashed

('rv( represents twice the measuredr(Tction c-r)ss sections obtained in

the present experiment and is a

measure of the total a-particle pro-

duction cross section.

A major effort in the past year has centered on attempts to

interpret the systematic features of the measurements in terms of the

underlying reaction mechanisms. For the (d,p) and the (d,n) processes

the description is based on a formalism in which a direct-reaction com-

ponent is added coherently to compound-nucleus contributions, while for

the (Io ) rva( t'in, the iit, r.o ta'n is e 3sojr11erI to proc eed through < or.:rund -

nil/ Ic-us levels, both nw;ar .inrd distant, of even shin and ;i~tive ;;.rrt',.

Alth-,ogh a c insist ont ite rret;1 ',tiwa of the available dl., td h..s so far bte-en

largely gnsuccessful (primarily b-crtusfe of the I:,rg numb'' r of p;ar;,rr etrs

ne ess;ry t- Iro o ru'.,' -'", . h;nra-is opcn in the relevant oiao rgy

garage), ;+ fo '. ate r tIn.! : . s haeve bice-an un(c ove reel. I he so- in( lurle1:

(1) the otiserv.,tion thaet - e yrpijcunfd-ie ooa < et rilboitions to the rca< tions in

the energy rf-gioln 'iii to 1 XleV :+ r( l:, rt4fly nonr-sin;-,,t in ,pite of observers

"peak-like" cx< it:otion fun< ta' , ,rd (.'.) unfi, r < o rt:ain < orift ions it. r -

fercnc a tbatwerIelit r t. and '<,monAatd ;,r), .o is subst-Atital " t 1t the

t r;eeiitioratl;a ;tppro;ac h thoit tr 1*o t:- i( K: -crno r v ('1, ) "+r, ('1 , ra) reo;( tiow-, on

light 1a( lei as or+ iTacoherornt ain olf stlch to rrms may 't - tlw;ays be va lid.

lu. rt},('r <( +al ;ottInn i ;r4 Duu< t otrg I:ted in or(d b r to (0< pl o t I 1thes4 st1nl a'

rlirairig th - 1 )r<'Se't frs ;gl y,-Io r.

1). _ >sn r I h roo - KoyI' roa k'a in d 4 ltos ftjijsi( ttLow Lr_1-r1 x

I. I.. I b-1 .m d, 4.. J. t l. . n, 1. a '.i : 1h.-1 , ( . 1. :a ,

I2. M -yer -:t Ihitrzmra ci st( r, Ma d 1. l'. M Brigra L

A ltr'g part (.t th tt.l ross s5((til(I for d + Ii r, tiors

Comt- frormi th rot )-b(Av br(;a I.(tt or+< t ess s: (a) ri 4- L -1 + It- + I-

and (b) d 4 Ii -+ ! II + lit. .t hav( mI ;asuartd an aI (r -i. riati Ons and(!

tot;l ( ross sc(tiOns t,>r tht- p rtdlltt s from both of thbst r'"t. tifl S to p rovlid-

d;ata for ev;alua;ting thti use of (1 - Li as fuel in controlled L1, hrmonuclh-;1 r

applications.

Because of the thrt (--body final st;a!( in tlhi e r+ etions,

the spectrum for each of the pa rticles is a contain m.la! T;tl cross s(( lions

were obtained at each incident energy by summing th( ( ontinuumn over the

final particle energy and then summing the angular (listributitn over al-gle.

The neutron energy spectra were obtained by timrn--of-flight techniques and

the charged-particle data were obtained with a combination of time-of-flight

72

IV. A b

tt< hniques wit}, h-t- normral pulse spectretia up) of Si .-irf t, t-b.arritr

d(ttei tf rs. The letter metasuremunts allowed us to) setpar;itt th. spet tra

from th*s re re A tions itt ( contributions t rom e.I h of th. leiwc 't Iuu r

mass . I hus wt obtdlc-d ttal ross seetoiOs 1o n, 2 r!.) *r'tans,

n - ( lie .rId 31) and 11.tss 4 " lie frun r;t tirn- (a) "nd (1)) .

TL -, t(t -I e rts s4 e tins tre < l #iIly nut ind pw dt 1 !t in that, for

*X;t1i:)!' , y 1 (m f nIit ron ;nd upreitean tot;a1 4'reiss s' t,t- t irIm (:)

ad (b) must be tq 111 I t th tt.al I ross s<< titans t,<r 1)ro(du, tie)n (if imn s -

l);t rti< les (an ;lso' total ross -,ctIfn for mass-i ;pa rtieles).

svmbolic, ;ll. have

(T (11) + r (p) n (mass 3) (mass -I (1)t t t t

in ;uil obvious nfot;iti',n.

'I lis rehlationshlt) forfli - th. !)Si S r a compare 5n a the

rniut ron measirmnenIts with th} (th;i rL.d -pa rtinl1 raasuremrnt .

have use! 1.ri. (I ) to obta iln a niOthe r mya slire( of the total cross section for

'1 '(t (2 4 (1) /2 (I)). (2)t t t

~th Yr (ni), obt ieel Iron 1~a he a n iutrion vii h, itn. o ( ), 1 obai e t rt 1

J. (2), a r plottfd(1 in 1 ig. 25 ;long. with '1(p) so th3t one can judi( the

degree O1 ( OnsistnC(\y btwe(I1 thw nitutrotn and charglt ed-particle dat;t. One

further piece of datt is a v.ailable in the form of a tritiun activation

mea :s-urcmett. 'he ( ross section for tritiurn activation should, of course,

("qual Qt(p). 1'he tritium ac tivation rnea suremnents are a lso plOtt(id in

Fig. 25. All of these intercomparisons are consistent within experim antal

error.

These results on the total cross sections and other data on

the shape of the continuum energy spectra, the effect of final state inter-

actions and the ratio between the proton continuum cross section and

1 R. L. Macklin and H. E. Banta, Phys. Rev. 97, 753 (1955).

.9-t "

*/

,4p

4,

-. ' '4

- )r 41)1 .r, NooA 1 1 ' A-V

f r pit ub4ll t t ji b In. ll 1 l').. s

I

1*

LIljOo

}. 19- Z5. 1 l..' ' .+"+l roj% s q.(< t i+n

for d + (.1 - + .: I,. (ipper

+ urve) ;,anI ' ' '.. + 3110 +

()(.w#r < urvo) a s ,t Nro tion of

dout ir-fin .ri b; rditg ne rg y.

1he upir < o rve di spl; .s point s

de-rivend btOtl f r':ri dirc t tnvas -

ur+"tr+-rt of th+" protgrnt < tntinturn

;4fnd froth mnetas ro in-rt of

t ritiirn b pr'du< t ion. PIoints fill

the low'r < urv' + orn' from (fi r'< t

trie;, sur .ni.rit of thb n+ utron

< 'nti111m nd ;lso lrurn 1mn4.+s-

u rern. ltts of t h4 < 4 rgeI -tI. rti ( If< )t ontna.

I , I r1 "1 1't i' 111 1 n );n cc I. -''4 I ) I)>, b b)? > 1n itt- *4

(4

(.1'0 I tj(jIls for 1.i - (t -I dl( db P1 t ii11 oh 1 4i lg I _' I.r. r 1 ."

A . J.1 f.lwt" yn 1 , f 11.. I ll nc, . ~ . ); D ,"ids, i . teyt"r"- huitz mtl isttr,

a nd I . w . ring

A ctomlipl t4 s1)cifit tin of thw r(c; ti vit of a d- ].i filw] 4

1)1:5I11; t r posSil1)14 thi' rt o rbc)l( 14 : ,pr p i< ti ons r (ciirs4 kno\ ,I. dgiL4 not (ally

Of thle p rit ry ( 4 i i < r"s : 'ti s bitt ii th1), r.111. st l i s for 1' ( -4,

t uris of t1) t 1Iroduct !ill< I- i ,wltIi t';It 1 th r .Ild '.it11 thn .i 1 11t m at ri'a 1.

In this c,)nnc'tion, cross >ectiors for th4 c r.;tiorn arid Iittraction of 3I

wvithir th, plasma b(corm- esp-( 1aliN important. >j)(rimnents hav4 bi'

performed in \which difftrential and total (a1gl -i!iratdI) < ross s( tons

6 3 (, 's 8have been obtained for the Li(p, Iie)r and Li( HII ,p) Pd reactionbs at

energies below a few i ('V. Cha rged-particle beans w re, after Accb 1c ra -

tion in the ANL Dynamitron, incident on thin targets of LiF ((-nriched to

99.3% in Li and evaporated on carbon foils) placed at the center of a

76-cm diameter scattering chamber. The yields for the outgoing charged

particles in the reactions at incident energies down to 0. 1 MeV were

74V*. At,,.

o0~

+

IV. A, ,tj

obtaintid .t anigits Uf 35 tt'

155 by us. of S surfat e- - -

barri er diett to rs, *nd < on- u:'. .

vt-rt. d Into .tibsollut, t rosy ""

- tions. Total < rosy

t . is we r. t. t. rtmio: t d "

from expansion of th.s .*

dift. ri-ntidl t ross s.< tiots

in a series of !.egnrdr. ..

polynorni;ds. 1- igure.

shows sot, of the res!'

for tih l.i',, r.

t1on. - - , '0. 9rt. .

wf ent rtIYsi ot ,ts*rve t

}li. I. 4 .tetion e ross se(tioln for the

E>)II , I( )r re;t tion ( ompa rid t. pr

-iit t: . in t I. 1"y low'. - ni ergy me;tsurer nt .

l orith r me;tsur< IHi nt. - t eni rgis 11p t M. V h1 ve beenI comI)ltt-(,(, 3 8

;.nl;tlysis of to-s. . xp1rimnent as w4l1 ;1s thos for the 1i( H-e,p) Be

re;t tit)n is in tprigr(Ss.

(. Itolariztioo of Na't1utruis in lIsospin-Forbiddeti (n n) RZt;ctionis

T. i . I.i! , trn Tld :\. J. wy

* "

--

*V1tt1 S

and

lt pl; rization of neutrons in isospin-forbidden (p, 11)reactions can provi(le a rneasure of the neutron width a cquired by an

isobaric ana log state via Coulomb mixing with neighboring T st .

An isolated analog resonance can contribute to the neutron pola riz:tt ion

only if it has a nonzero width for decay into more than one neutron ( hannel.

In this case, however, a simple and unique prediction can be obtained for

the behavior of the polarization cross section as a function of energy and

angle. Neutron polarization cross sections have been measured for the

II

55i

Mn(p,n) le rea< tion, .at protnon vnergie(s corrEss.pfnding to ;an;ilog states

ill 1 e. I hte s polarization rne;aisureme-nts exhibit the predi< ted beh;,vior

;ind t has iridil.te th:t ;n -in;alog rSoflnn( *n a ( ; qJire ; ni'fn-negligibtle

Ie 'it r un :a dthl. We hiavv p revir as ly rep' rted similar r re sn lts for th '

V(; , n) ( .r rca. tion; however r, th int- rpretsation (-f these d;atta was

compli< .at e by the ;apparent exist *nt e (f tw( ('lese1y-Spja( ed ,ialog st:te

in the energy inte rv;al of inter- 1. It would be o inti rest to --:tind measure-

meits (f this kind to high r ext it.tati'n energies ;ind hea;.vi, r t~arge t niv lei.

A pa;p;;er 1e- ribing this work hae s bee in saiat tecd for puibli -

< t 'iln in Nu< 1. 1 hy.-.

(. I};,dittive ( lit irte 'i (_ ) 1:. '1 bro g th l .U t2- arnd 1(,.')2--MeV

T. .1. 1(wl("s 1-11( G. ; . G:, rv(y

WNe h:,v' a>mp1 , a tia lysis ', 1 cii tme aso r - 'a rit (>f tIn

r;adi;ative' wi,t hs (f t h- ( >. 6>-1 . 1 t1V d(')oblt tO th. broadi 2 level at

2. () MX1 V iI 1 . I'he widtIis 1 1- . . ara :.ia r;adlitative a Iaptaare of

)..-3(-.-(V alplaa paerti( 1ts fr(,i thi L'rinc(et(,aa Uniiversity AVi- , l<ot rota

in< 3(11it on ;i ;a t, -( I t I rgt t. 'Ihe g amalra;a rays w re (ob rvt(I 1 ;a

25 ('m7 " 25 'am Na I1p t rnna tar Irtim Brookha;aval N:tion aII-al r;atory.

Use of fast timiniag tethniI1(oIit with tl( puls e(I dv lot ruaa ban alow separ;a-

tiOn by time of flight batw(cn Last nialtros ;aind g;aramn;ia rays ruin th'

target. lb. obsa rvt-d g;arnn;a -ray sp(t lrin gatt-d on prom pt g;amnt r;avs

fromaa the ta rgat with the tharnma I ii utron background subtr;atd is shown

in Fig. 27. Angula r distributions Vra nasLirs((d ,t th iwak(ts of th.

16.6- and 16.9-ieV rasonanc(s and along with tli me;surad shape of the

excitation function determine. the mixing raati (s

[l'(1"2, T = 1)/I(M1, T = 1)] 1/2 0. 19 0.03

[F(E2, T = 0)/F(M1, 1 - 1)] 1/2 = 0. 22 0.03

[F(MI, T = 0)/'(MI, T = 1)]1/2 = -0.04 0.02

Submitted to Physical Revie C.

1 '

I ig. . ak magm tism (b)

1( Gam %v- 'I I r (, ) feri

1. trs. I he errors shslt own

fur th. veek -i ignitetism1

r oturm f ;a ti r , re st;tistic . l

wvith1 Ht backgr,, ind - bi-

t r:i t d. I he gIre -

stat r n -itn- oe ;t 1; .

\1 e\' i:- <lie rV . is i Wle.

;i we find the is<, e V (t : '' r,(+;tive v-i(dth t> '

, 1( ' .r .

h. <> ~!; -" '( vetet ,r , urr(-nt ih i v ( 9 ) r' ates tht-

iso-. ,r V anI ; 2 r',(di;,ti( - widths t(, the w(ak tnagnetism -nd see'nd-

If)olridd,:: . ,<r f(,rne fa< t10r , respL('tivelV, in beta (itcay. Ihe energ\

dlepenen t o! the weak rn;gnetisn form fact is determined via CVC

iron (:ur :asur .- ed ;m1ma - ra speet ron (after (Ie nV: lutA the Nar

d(ett( tor re' >) ('! n e) ;mnrl is shown in 'i. 2s. Ti" ,nerg\ *p( 1A(1dc c the

G;arnw-'Ie (Ir fterm factor is also show in Fi :. 28 from which we see

that the radiat(i' and beta d civs populate the final state n Bc (Lerentil.

I he meas urernnts of the weak maignetism and Gamow-1 el r form 1 tors

1). II. W\ilkinson and 1). F. Alburger, private commirunication.

and th. 1.2 r;:ditive width provide, in ( otjun' tior 'th tih tte*;sired Z -(t

:*ngilar correl;tions in 4ILi and 8i (P4f. 2), d rtodel -iniderneandert t -st tor

the- e:astefn, of se( nnd-< ass < urrents in Inr ss . We find th;,t vi /A,

1.4t 1. , jihere #1 is the se, aid -tl.s ind'u( eid-tensor form fa tor,

A 8, .,n< i tihe (;.rnow-'I 'iler forrma f:e tir. "I hu , ,r resqlts .re

1,1si t at t h.1 the ;g bseme. t" f f set On -( l ss ( urr nt :. .1d the v lidit' ,f

( VC for both th weak magnmtisrn and second-f1rbiddlen v eto r form

f;u lt rs.

Spl.a to i1ietclsure tihe ener-. depeanierae 1 (f th1 :.L

strength using the new Nal (lete < tors built : - r t \ ,r2 nn ; I.e. ar. i '-

mrn 1t , in con i n I tion with a n-w j$-us angul. (rr'; .. ' " 1 '' ' r.t

under wav ;at Argonaze, will provide . test of ( :V(: f(r the we;,k magnetism

and see tjni -fe.sbidldera ' t r f(arim fatcet<-rs ,s a fun ti-, of eni-ijuint

en cr g .

P. I:. T ribbl .- nd .' . G rve , :'h s. Ptev. '1i ., 9 7 (1 7 .

f. 1)( t i nd ( t ')- Arngulh, r ( >rrelations

. M c teewn arnd G. 1 . Ga r'e'ev

An c-iperiment to une,.-ur, tHit- i -(1 angular corre(ations as8 8

a fui< tioln of efnd-ptoint 1't1nrgv for the dtecay of Li and P is in progret s.

As the final sttte (41 the's (e<I, :j s is in the 2, c OntiluulM, there exists a

dist ribution of Eid-I int en' rg. Atinlysis of the spectrum of a p;,rtirl(es

following ti ) dca'ay a ndl th p <>n spet tr1oI1 from th, r;aiiati'.'a decay of

16.9- and 1 6. 6-M '. esonan, es shows that th, r1l m tive ('(nt ri)ution( of th.

vect'ar de( ;y is '- 10n' tion of end-puirt eneruw. ;-'hould these ::,)arin''aats

show det ail d agrec n aut as a fin( tion of einrg bet wecri n t idi vi Iuia I

weak form fao'ors and t'ie(ctrOCr1 ;lcti form factors, it .':ufldl t convincing

corroboration of the conserved--(ictor--current h''puthesl ;1 nd til ;absenc (

of second-class currents.

Preliminary data have been obtained for IA arid B decays.

When analyzed independently of final state energy, the f -(j. ;angular

Fig. . hE avurag difteren< e in . . '

c.reargies of alpha partit les it.

(Oin< idenr c- with 6. r -%1 tV pasi -

runs at I+ 1 41S ftr 'B --

d i* . ->1ottei . c 4x< it.tion ener{ :

of the final st -te in . [he -solid urvo-s Ltbtelcd 1~ :nd G

a r, the ext~a' ted r.tsults for

>- a. rm i :nd tfG iTY,,' - I !ller d* .ti y,4

re yn ;, ti V]v.

< rrf"tlations ar. in :approxirmiata. t gretmint-t with previous results. As

shown in I" it. "1, arin.tlsis of the t incidett at spet ra india .at as the decav

tO b, p. r t.loV I aler f, r :e *x< itttlitn EniirgiIs !a ,, th.an K M 1 .

IPossible ',iir< es t) sVsta- , t tr r- : 'ha $ -. .Iagul:-r < rrtlatioin

measure' t .w .:r, - urreunti. living tfnvfst. ted, and we eXI)e< t to collet t

final data in 1t476.

g. I'; ritvV ,l;ttiion in the r. 1 -\IeV Oaa l Yt < f B

S. . far-drnar, ( . \. C;agli;iri, G. I. rv , i. J. Bowh ,*nc . '). K1 1 aatwni

At the rnomnt ntext to nothing is known about the weak

neutral cur r- ,1 .!; .ulved in pn re l hadronic interactions. In a nuclear

s v. - , hen the pt rity-rmtixed leval di !!t'r by one unit of isospin, the-

effc t >he rhK rge-chinging wa a k < Frt is suppressed by a fac tor of 20

so that )nt has the opportmnitv to ma;u sure the parity mixing cause-I by

the hadronic weak n ut ral current. A favorable ease is the 5. 1 -M(AV J:2

parity doublet inl 1n1, where a mea sure ent of the hclicit\ dependence of

the rate for t'h, L.i( i, y)itB reaction provides a v( r, sensitive' test f, r

neutral currents. This experim tnt is now being undertaken. Pr tli ina rv

studies have shown that ani ixperimrrnent sf'nsihvu to effects at the }t~vi

predicted by Cahibbo theory, without the enhancement from neutral

Stanford Unive rsitv, Palo Alto, California.

Princeton University, Princeton, New Jersey.

currents, is porssiblle with a polarized Li target oTn rnune1;iyer thick.

Construction of the polarized target, using atomic -bearn te, hniques to

provide the polarizati on, is under :., t the pre sent tirm- and should b-

completed this < oming spring. At that point, measurements will begin.

h._ kdi etive C;Ipteure of Alphas on f)euteriurn

'l. .1. fowles, ' . G. 1I. Pobe-rtsoi, ' 5. A. Wa rne r, . I).er, and

V. M-lin

We have nieasured the r:,di:tive capture ''f el parties on

deuterium from 3. 3- to '/. K-MeV excit;,tion energy. Alpha p; rti les from

the '.1i higan Stat e Un .'r ity < ' lot rozn are inr ilenit on ;, thin de terat-d

p(lye(thylene target ; !.! i, re oiling Li are dete- t4e! it 01 in thle- onge

split-pole spiedrographi. Pileup reject tion of suAttered U 1;perti( les has

been improved so th;+t ba; kground levels are below 1 ni. Ihe- measure

t-xcitatiri funt tion is shown in 'I abl- II. The hi rease in < ross set tihn

.ra ove- -1. 1 MeV is Ir!:eiiteed to (i ret tTA MAL'. 11. %1 et"i re-d

ew ss se( timn of d((,N1)'li. 1-.1 redi.tive- . .;eptur I r rr <uiltitiuul

1 he qu t cd c rro trs a rv st a-Ibe fite Cie tstate-s into the , 1 1 . !ate -tisti' ;+l n]%.

-1Me-V. Ihe angul.er distributi~! 2 the

I- (MeV) n (ni) (lecay can be obt;tine-d from the- mcas-

---- - - -------- - IFred (n(rgy of the I re ui1 ions an

?. 3 17 'ithe p'( itio n spectrumn 1,r the run ;tK -4. 1 ae V (ne ;r the pc-ak of the 2 ,

s 0 State ;it .c 2 in Li) ( onfirrn

2elEctron sca'erim:L nit ,lirermeurts

4. 8 36that show th (1'.( i, : re t (i;U!drunOle

i. -i 10in charter. EH:. mw Sire-t rire'(

9.8 5) I

Michigan State University, East Lansing, Michigan.

1 D. NI. Skopik, E. L. Tornusiak, E. T. Dressler, Y. M. Shin, andJ. J. Murphy II, Phys. Rev. C 14, 789 (1976).

s

.ipture < ross set tion is of astrophysical interest .,nd . grtes with calcula -

tions of the t < sr aic abundance of Li.

Wv are now .ttrnTpting to measure via radi ttiv e .a:) tre the

(i-p;*rti< l- width of the 0 , I I state ltt 3.6 e\'. ( epture into thi- level

i, forbidden h- part% and isospin c onserva.titrn, buit L .1 <0 , W'

. I I p rity--. olitmi hadroni interact tiin whit h :,i1e " me t: the- 1 , !

st re-nLth. in the < JtinIuum with the 1.;-MV ltvcl. This hidrni, itnt. r-

at ti'1 n should be strunglv etihant ed (b\ a factor of 100 in th. rate) by the

presence ot neirut ral cur rent s. Const rut tio of a I). () gas jet ta rjget h Is

been complete; and with improved be;mline optics ;md more intense

-8 -7alpha beams, we ho pe to measure the predi< td alpha width -f 1t - 10-7

e4V.

.' r,, in Inte ra< tiufn itur.t Nu. 14i, chted by ii. Jot him andB. /it gl-r (North-holland, 197 ,.07.

i. Sear K f r ! ivlht P'.es udc,.!, * r liosons (Axions) in Nu< lear I r nsitions

W. lie .,i , . . '1 K r ,, 1I. ,'11l, ;rad J. '. t hiffer

1e ent thee

adtl Wi': 741 for the ex ''

sc a. r :>a)r1, i whic h the

< :;, . - m r ;kl, ttt !> rv

rtnsitions. : he sel(cti(.

tnd ve have calculated the

I-

1*M1

2)G; NM

I6 (

retic;,l :L',estions have beeni made by WVteinberg

nce of a light (rest m;vss t100 ke\'/.) pseudo-

have named the axion. I his particle would

:n :frd could thus be p)roduce d in nuclear

n rules favor ( rametition with Mli gamma enissio!,

br;trching ratio to be

Si~Z 10 (1

sI1

assuming a quark mass (m ) of 300 MeV. Possible 'xperimenis to search

for axions are being investigated. A possible measuremunt nfea r ; reactor

was explored. Here the ;ixions would be produced in competition witi

gamma rays from fission, neut ron t apture, and radioactive decay. We

82 IV. Ai, j

found that the most sensitive experiments would be very similar to those

for v-e scattering that have been performed by Reines and co-workers.

From the background seen by these authors we were able to set an upper2

limit on the axion rest mass of ~30 keV/ c

A complementary experiment that would make use of the

Mossbauer effect and be sensitive to axions with small rest mass is being

explored. Feasibility studies are in progress for several favorable

transitions.

j. Search for Fractional +1/3e Charges in Nb, W, and Fe Metals

D. S. Gemmell, F. P. Mooring, T. R. Renner, and J. P. Schiffer

The recent report by LaRue and Fairbaink of an ap )arent

observation of fractional 1 /3e charges on Nb spheres, :,nd earlier

negative results from quark searches at Argonne,2 could conceivably be

reconciled if a +1/3e quark were stable. Such particles wo'id be loosely

bound in most metals and diffuse through them readily. NI), W, and Fe

metal filaments were placed in the terminal of the Dynamitron accelera.or.

With the terminal at i MV the filaments were heated and any positively

charged particles accelerated into a Si surface-barrier detector. 1 he

charged particles do not pass through any impressed magnetic field so

there should be no mass-dependent deflections. Particles of 1/3 charge

would have an energy of 0. 33 MeV and produce a corresponding pulse in

the detector. Fewer than ~10 particles were seen to be emitted below the

temperatures where alkali-ion emission from the filament become

excessive, giving a tentative limit, under this hypothesis, of 10-22

quarks/nucleon. Ihis is an order of magnitude below the value implied

by LaRue et al.

1G. S. LaRue, W. M. Fairbank, and A. F. Hebard, Phys. Rev. Lt.38, 1011 (1977).

C. N. Stevens, J. P. Schiffer, and W. A. Chupka, Phys. Rev. 1) 14,716 (1976); W. A. Chupka, J. P. Schiffer, and C. M. Stevens, Phys. Rev.Lett. 17, 60 (1966).

IV. Ba

B. CHARGED-PARTICLE RESEARCH AT' .E TANDEM ACCELERATOR

The light-ion research carried out at the FN Tandem has

covered a wide variety of topics. More recently, there has been a focus of

research activity to fewer areas.

Over the past yea r, significant progress has been made in

nuclear-structure studies in the f7 / 2 shell using the (a,ny) reaction andrequiring time-coincidence detection of the n and y events. Very suggestive

regularity is seen in the excitation energies of low-lying positive-parity

states in 4 3 Ti relative to their excitation energies in the mirror nucleus4351

The research into the properties of new isotopes of astro-

physical interests in the Fe region continues, by use of the techniques of

@ and y-ray spectroscopy. The 1 8 0 1f(p, n)1 8 0 Ta reaction was studied as

a possible source of 1 8 t'Ta in stars.

The development of the la rge (25 cm diameter by 30 cm long)high resolution, (2. 3% at 17 MeV), NaI gamma -ray spectrometer willlikely cause a resurgence of activity in studying the radiative capture of(L particles to try to find convincing quantitative data on the giant quadrupole

resonance.

A review article on our extensive program on studying thesingle-particle structure of the actinide nuclei was published in theReviews of Modern Physics this past year.

a. Single-Pa rticle States in Actinide Nuclei

J. R. Erskine, A. M. Friedman,* I. Ahmad,. and R. R. Chasman*

A program to study single-particle excitations in actinide

nuclei has been underway for some time. Magnetic spectrograph data on

the (dp), (d,t), ( He,d), and (a,t) reactions for many actinide targets

have provided extensive knowledge of single-pa rticle states. 'This basic

knowledge is of crucial importance for the understanding of the spectra

of excitations observed in deformed nuclei in the actinide region. An

article summarizing this work was published this past year in the

Reviews of Modern Physics.

*Chemistry Division, ANL.

83

IV. Ba,b

Due to the interest of groups at Prookhaven and Grenoble

who use techniques based on neutron capture, previously unpublished data

from (d, p) reactions on 237Np and 238U have been analyzed and prepared

for publication. The expectation, especially in the case on 238U, is that

these studies with a variety of sophisticated techniques, will reveal new

features of the coupling between single-particle and phonon degrees of

freedom.

b. Comparison Between the Decay Properties of the Isomeric 19/2 Statein the Mirror Nuclei 4 3 Sc and 4 3 Ti

L. Meyer-Schtzmeister, G. Hardie, A. J. Elwyn, and K. E. Rehm

The decay scheme of the 19/2 state in 43Ti has been

established recently. Although it is very similar to the well-known one in

the mirror nucleus 43Sc, the reduced transition probability B(E2) of the

19/2 states and the excitation energies of the states with spins 19/2~,

15/2~, and 11/2 which are involved in this decay show distinct differences.

The observed shifts in the excitation energies can be qualitatively under-

stood by assuming that the interaction energy of two valence protons is

different from that of two valence neutrons. Calculations have been per-

formed by R. Lawson and by B. A. Brown to evaluate these energy shifts

from the data of neighboring nuclei. Reasonable agreement was obtained.

From the measured mean life r = 810 50 ns of the 43Ti 19/2 state,

a B(E2) value is derived which is nearly a factor of two larger than that

of the 19/2 state in 43Sc. This is in very good agreement with calculated

B(E2) values which are obtained by using the (fp)-shell model and the effec-

tive proton and neutron charges derived from the measured B(F2) values

of the 6+ -- 4+ transitions in 42Ti and 42Ca, respectively.

*Western Michigan University, Kalamazoo, Michigan.

84

IV. Bc

c. Positive-Parity States in 43Ti

L. Meyer-Schutzmeister, R. E. Holland, G. Hardie,' A. J. Elwyn,S. A. Gronemeyer, and K. E. Rehm

Positive-parity states of 43Ti were studied in the40 43

Ca(r,n) Ti reaction with alpha particles of 20-MeV energy. Using a

pulsed beam, the mean life of the 3/2 state at 313. 0 keV was measured to

be r = 18.2 0. 8 s. Gamma decay of the levels in the mirror nucleus

4 3 Sc suggests that positive-parity states in 43,Ti, and only these, decay to

NEGATIVE PARITY STATES

f7/2)

(keV) J keV (keV)

690nsec / 57 810nsec2987.3 -- -- 15 . - 95

28 _ - _ - 1 571830.0--- -/2

0 - P-7/2'- - - -0

(o, b) (b)

POSITIVE PART ri STATFSI 4

keV J3755---- 52

?14 3 ------- 4--(

25532)

keV key3C- - - -2062

45 148433 7-- 712'

142 -'C22 488C 2" ,T 999855_ _+ 144

II

j 61 3 ~152.0 -3/2*, B Sec

0 - c6 36 sec

C 72 4 3

T

(C) (b)

Fig. 30. Level scheme of the positive and negative parity

states in the mirror nuclei 4 3 Ti and 4 3 Sc. (a) Z. Sawa,J. Sztarkier, and I. Bergstrom, Physica Scripta 2, 261

(1970). (b) Present work. (c) R. F. Holland, F. J. Lynch,and K. -F. Nysten, Phys. Rev. Lett. 13, 241 (1964); G. C.Ball, J. S. Forster, F. Ingebretsen, and C. F. Monahn,Can. J. Phys. 48, 2735 (1970); and A. R. Poletti et al. ,Phys. Rev. C 13, 1180 (1976).

*Western Michigan University, Kalamazoo, Michigan.

85

IV.Bc,d

the ground state predominantly via the isomeric 3/2 state. Hence the

gamma rays emitted from positive-parity states were selected and studied

by measuring a gamma-ray spectrum in coincidence with the delayed

313. 0 gammas. These measurements suggest a level scheme for the

positive parity states in 43Ti which, together with that of the negative

parity states, is shown in Fig. 30. A comparison of these states with the

corresponding ones in 43Sc, also presented in Fig. 30, is interesting

for two reasons. First, the energy difference between corresponding

states in the 43Ti 43Sc pair is rather large (~145 keV) and approximately

the same for all observed positive parity levels. It can be understood in

terms of a reduction in Coulomb repulsion in 43Sc due to the promotion of a

d 3 / 2 proton into the f7 / 2 shell. Second, the energies of the positive-parity

states behave like those in a rotational band built on the 3/2 level. These

two properties are not observed for the negative parity states of the

43Ti- 43Sc pair confirming our suggested level scheme of positive parity

states in 43Ti. Finally, the B(M2) values for the 3/2 states in 43Ti and

in 43Sc, derived from measured lifetimes, are found to be equal within

experimental uncertainty. The value for 43Ti is in agreement with calcula-

tions1 based on single proton and neutron reduced matrix elements derived

from the measured lifetimes of M2 transitions (7/2 - 3/2 ) in the mirror

nuclei 9K and Ca, but disagrees with shell-model predictions based on

the use of pure wavefunctions.

iR. D. Lawson and A. Milier-Arnke, Phys. Rev. C 16, 1609 (1977).

d. Investigation of the 45V Nucleus

L. Meyer-Schi tzmeister, S. A. Gronemeyer, G. Hardie,*X. J.Elwyn, and K. F. Rehm

The comparison of measured properties of mirror nuclei

often provides detailed information on nuclear structure. Experiments

have been initiated which should provide information on 45V (of which

*Western Michigan University, Kalamazoo, Michigan.

86

IV. Bd, e

hardly anything is known), the mirror nucleus of the well-investigated 45Ti

nucleus.

(i) Prompt and delayed n-y and y-y coincidences have been

studied in the 40Ca(6Li,n)45V reaction using a 13. 5-MeV Li beam. A

gamma ray of about 55-keV energy seems to belong to 45V but no further

measurements are planned since the cross section of this reaction is too

small to give a useful signal-to-noise ratio. However, preliminary

studies have shown that the 4Ca( Li,2n)45V reaction is much more

promising and prompt and delayed n-y and y-y coin( idence measurements

are planned.

(ii) A lifetime measurement for the 3 decay of V has been

made by using the 10Ca( Li,n)45V reaction with a pulsed Li beam of 13. 5-

MeV energy. Preliminary results suggest a mean life of 412 20 ns,

a value consistent with a superallowed [3 transition between mirror nuclei.

Such measurements will be repeated not only to measure the lifetime for

beta decay, but also that of any low-energy gammas that may follow the

445beta decay if the transition fromt 4V does not leaid to the ground state of4 5

Ti.

e. g Factors of Nuclear Levels

R. E. Holland, T. V. Raglande and R. P. S( ha r( nberge

Final data were taken on the g factor of the first excited

state of Mo (E = 99 keV, T1/2 = 17 ps). This is the last of a series of

measurements we have made on long-lived isomers. In this case, data

were obtained for both a liquid (Zr-Cu alloy) target with the reaction.

96Zr(a,n)99Mo and a hot solid metallic target with the reaction98 99

Mo(d,p) Mo. An average of all measurements gave g = -0.310 0.001.

In addition, we observed for the solid target a sudden increase in the

number of Mo isomeric nuclei participating in the Larmor precession

Purdue University, Lafayette, Indiana.

87

IV. Be,f

when the temperature was above 1100 C. This undoubtedly represents a

temperature at which the defects (created by recoiling Mo) could diffuse

away before destroying through their fields the spin alignment created

during production of the Mo. A paper is in preparation.

f. Studies of Nuclei Far from Stability

This program involves the investigation of new unstable isotopes

far from the valley of beta stability. Properties of nuclei of interest to

astrophysics near iron are being measured using P- and y-ray spectros-

copy. In the past year a new line of research has begun: the study of

0+-0+ superallowed @+ transitions on the N=Z line. The information ob-

tained from this work is of fundamental importance to theories of the weak

interaction, as well as providing a testing ground for our understanding of

small corrections to the Fermi matrix element due to isospin mixing.

(i) Mass and P Decay of 57Cr

C. N. Davids, D. F. Geesaman, M. J. Murphy, E. B. Norman,R. C. Pardo, and S. L. Tabor

The mass and P-decay scheme has been obtained for 57Cr

(T 1/2 = 21. 1 1. 0 s). A feature of thiL study was the fact that the ground-

state-to-ground-state @-branching ratio was extracted. This was made

possible by the fact that the half-lives of daughter and parent are similar,

and the direct daughter production was not much greater than that of the

parent. 57Cr decay resembles the decay of 55Cr, except that many more

states are populated. The measured ~ Cr mass excess, -52. 39 0. 10

MeV, is slightly more bound than was predicted by the modified shell-model

mass equation.

The final decay scheme for 57Cr is shown in Fig. 31.54 57 1 57

New information from the Cr(Qp) Mn reaction on spins of Mn states

has allowed the assignment of 3/2- for the spin and parity of the 57Cr

ground state.

K. A. Aniol, D. W. Gebbie, C. L. Hollas, and J, Norzynski, preprint(1977).

88

3/2- 21 ItI Os

2 47Cr 33

0 = 5 Ito I Mev

A,

4O

3/2,5/2 - - - - - -- 2702 2

35/2 O p - - - - - -- 2a 3 4

3/2,5/2 -0 4j -- - - ---- -275 6

~3/2 -)/ \Y +'1w- - - --- - -- 2232 9

3/2.,5/2 -496 7

3/25/2 - - 356

3 2-5/- -

I/,/ - j 1 V1 Ol 46

3/7.5'? T' I44T T TT7TyV - 49? 7

3/2,56/2 # tom+t+* -- 7

3 '2 +4

I ,,

I I 1 ,

57Fig. 31. P-decay scheme of Cr. Also shown are levels

in 5 7 Mn from the 55. n(t, p) 1' anIC 5 Cr(i, t ))' 7 M1n

reaction.

(ii) Sup( allowed 0 -+0 Ft ermi T ransition s

C. N. Davids, C. A. Gagliardi,* N. J. Murphy, old 1. B.

Norman

The study of superallowed 0+ -)+ @ transitic'ns between

members of an isospin multiplet yields information on the weaks vc.ctor-

coupling constant GV. The equality of the ft values for all such transitions,

apart from small radiative and charge-dependent corrections, is a

necessary consequence of the conserved-vector-current hypothesis.

Much experimental effort has gone into precise measurements

of the half-lives and total decay energies for the 18 or so known cases of

Princeton University, Princeton, New Jersey.

IV. Bf 89

Ig (/.)

2 5 0.3

6 t0 I

0 3 02

040 1

S2 0 5

02t01

6902

55t0408t03

Q4 02

Log h

5 47

581

6 75

6 585 846 92

5 62

7 19

5 896 75

708

-

5/2

3 2

2640260 7259

202___03

24

-- - 347

--- - ' s6

23?

-5

2008' -9621928,9,61837

'26

536'493

-- - 477175

X57

851

2'203 6 .4

2F3t1 8 6.55

-01 '44

7412 546 5 2-Mr

84

IV. Bf

+ -10 620+ -0 transitions, ranging between C and Ga. We have begun a program

to extend the masses involved up to A = 70 by attempting to observe the sdecays of 62Ga, 66As, and 70Br. These nuclides are expected to have

J = 0 , T = 1 ground states, and thus will decay to the 0 ground states

of the daughter nuclides by energetic positron emission. They are par-

ticularly interesting because the i sospin-breaking electromagnetic interac-

tions should cause observable effects.

The first nuclide that has been studied is 62Ga. It was

formed via the 58Ni( Li,2n)62Ga reaction, with a 24-MeV Li beam.

Energetic positrons were observed with a AE-E telescope consisting of

a 0.02-cm deep by 2.26-cm diam silicon surface-barrier detector and a

1. 1-cm deep by 3.57-cm diam intrinsic Ge detector. After requiring a

fast coincidence between the 2 detectors to reduce sensitivity to y rays,

the energy in the thick detector was accumulated in a two-dimensional

array along with the time since the end ,f bombardment, in 15 ms

increments. In this way both time and energy spectra could be projected.

Figure 32 shows the time spectrum for the events having energy greater

than ~4. 5 MeV. The solid curve is a fit using a decaying exponential

plus a constant background. The mean half-life extracted from a number

of such curves is 115.7 1.0 ins. Figure 33 shows the energy spectrum

for the first 3 half-lives minus the spectrum in the next 3 half-lives.

The solid curve shown was generated by extracting a spectrum shape

from the decay of 193 ms--54Co and stretching it to fit the 62Ga spectrum.

Energy calibration was obtained by also fitting the spectra of 46V, 50Mn,

and 58Cu. The measured mass difference between 62Ga(0 ) and 62Zn(0 )

is 9. 120 0. 050 MeV. Oni then obtains, after making the above-mentioned

corrections, a corrected'" ft value of 3132 96 s. The value extracted

for the lighter mass decaysl is 3087 4 s. These values can be compared

1H. Vonach et al., Nucl. Phys. A278, 189 (1977).

90

Ua,E

Vt)

z0U

10000

5000

2000

1000

500

200

100

50

20

10

5

2

0.0

Fig. 32.great rdecayin

0.4 0.8

TIME (sec)

1.2 1.6

Time spectrum of P+ particles with energies

than 4. 5 MeV. Solid curve is a fit using ag exponential plus a constant.

FIT TO BACKGROUND SUBTRACTED 62GA SPECTRUM

1000

z00)

900

800-

700-

600

500-

400

300

200

100

0'0

?i

LJJV L I I I I I40 80 120

CHANNEL

-1

-1

160 200

Fig. 33. Energy spectrum of @+ particles for the first3 half-lives, after the spectrum for the second 3half-lives was subtracted out. Solid curve is a fitusing the shape taken from the decay of 5 4 Co.

IV. Bf 91

TIME SPECTRUM - BETA E > 4.5 MEV

I -

I-

IV. Bf

2with the previous measurements of 116. 4 1. 5 ms for the half-life and

9. 3 0. 3 MeV for the mass difference.

The precision achieved so far in the present work is not

quite high enough to test the validity of the charge-dependent corrections.

Work is continuing with the aim of improving the precision of the

measurements.

2R. Chiba et al., submitted to Phys. Rev. C.

(iii) Mass and Level Structure of Ge

M. J. Murphy, C. N. Davids, E. B. Norman, and R. C. Pardo

In connection with the study of the (3 decay of As, the

mass excess of 67Ge has been measured to be -62666 t 12 keV, and its

low-lying odd-parity excited states have been identified (Fig. 34). Included

among these new levels is an isomer at 18. 2 keV with a total mean lifetime

of 18.5 0. 3 fis. The lifetime of this isomer has been compared with

that of known isome rs of five

neighboring N=35 and N=37 nuclei.

") ~There is a systematic trend observed

808.1 e 3/2) toward longer lifetime with the

addition of neutron pairs. Theoreti-

cal calculations using explicit shell

and quasiparticle models show this

0 o trend to be consistent with the known

243.6 -. (3/2-) short-range pairing force in these

122.7 (3/2) nuclei. Future plans include

18.2 m- ~ 4 (512-) tr18.5s measurements of higher energy6 7 6732Ge35 levels in Ge which are of impor-

67 tance in conjunction with work onFig. 34. Level scheme for Ge, 67

obtained from the 6 4 Zn(a.,ny)67Ge As.reaction.

92

IV. Bf, g

(iv) Mass and P Decay of As

M. J. Murphy, C. N. Davids, E. B. Norman, and R. C. Pardo

The new isotope As has been produced, and its s+ decay

to 67Ge observed. Its half-life has been measured to be 42. 4 1. 2 s, and

from the (3-decay spectrum its mass excess has been tentatively deter-

mined to be -56. 750 0. 1U MeV. A partial decay scheme has been assem-

bled; its completion awaits further investigation of levels of high excitation

in 6Ge.

180g. An Invest- gation of the Ground-State Yield of Ta Produced bythe

18 0 Hf(p,1 1 8 0 T reaction

E. B. Nor r '. R. Renner, and J. P. Schiffer

Fruri an astrophysical point of view, 180Ta is a very

interesting heavy nucleus because it cannot be produced by the standard

nucleosynthetic processes. It is also of interest to nuclear physics because

of its (8 ) ground state and low-lying 1+ isomer. The isomer beta decays

to 180W and electron captures to 180Hf, but does not decay to the 180Ta

ground state. As a result, any reaction which produces 180Ta in its

isomeric state will not contribute to the observed abundance of the long-

lived 180Ta.

One of the proposed production mechanisms for 180Ta is180 180

the Hf(pn) Ta reaction. We have measured the thick-target yield

of the 8. 1 hr 180mTa produced by bombarding 180Hf with 8.0, 8.5, and

9. 0 MeV protons. The yields of the 93. 3- and 103. 6-keV y rays and those

of the characteristic K x rays were measured using a Ge(Li) detector.

Using the results of these radioactivity measurements and the previously

measured thick-target yields for (p,n) reactions on a number of targets in

this mass region, we have calculated the yield of the 180Ta ground state

by subtracting the activation yield from the interpolated (p,n) value. Our

preliminary limit for the fraction of the (p,n) yield producing the ground

state is 40.3.

93

94 IV. Bg -i

In order to learn more about the structure of 180Ta, we

have also performed 11fa(dt) 180Ta and 180Hf(p,ny) Ta experiments.

Twenty-three levels have been observed in the first MeV of excitation and

number of gamma-ray transitions have also been seen. Analysis of the

data from these experiments is cur rently in progress.

h. Search for Neutral Currents in Mass 20

T. J. Bowles, R. G. H1. Robertson,* -'P. 1yer, and P. MelinT'

We are attempting to m a su re the alpha width of the 1+,

T 1 state at 1 1. 233 MeV in 20Ne. The alpha decay of this state can occur

only due to a AT=1 parity-nonconserving hadronic interaction. This

interaction should be strongly enhanced (by about 100 in the rate) due to

weak neutral currents. Since essentially nothing is known about this

interact tion, the n (a surement of this alpha width provides an opportunity

to learn a great deal about the weak interactions.

This level will be formed in the radiative capture of alphas

on 0 and the recoiling 20Ne will be detected in a recoil spectrometer

which has been designed and which will be under construction shortly.

We expect to be able to measure an alpha width of less than 10-5 eV

while the theoretical prediction is 3 Y 10-5 eV. We are also investigating

the possibility of measuring this alpha width by photodisintegration of 20Ne.

i. Nal Spectrometers

T. J. Bowles, H. E:. Jackson, Jr., L. Meyer-Schutzmeister, andR. 1. Segel

We are completing construction of 2 large NaI crystal spec-

trometers. The spectrometers consist of a 25 cm X 30 cm Na! crystal

viewed by seven 7.5-cm RCA 4524 photomultiplier tubes surrounded by

a 5-mm-thick LiH shield for thermal neutrons. This assembly is sur-

rounded on the sides and front by a t 1.5-cm-thick plastic-scintillator

Michigan State University, East Lansing, Michigan.

IV. Bi

anticoincidence shield which provides rejection of cosmic -ray events in

the crystal and improves detector resolution by rejecting events in which

some of the radiation leaves the NaI crystal. A 10-cm-thick cadmium -

saturated-lead shield surrounds the entire assembly.

Initial tests show that both spectrometers have ;i resolution

of better than 3% at 17 MeV. The best resolution obtained so far is 2. 3%

at 17 MeV from the 11B(p,y) reaction, which is better than any other system

reported in the literature. The resolution at 20 MeV at a counting rate of

250 kHz is better than 5%. Further improvement on these results a ppt2 rs

possible.

The spectrom eters have been used in ail exp eriment at

LAMPF and will be used in continued work at LAMPF and at Argonne in

radiative capture measurements and in studies relhited to fundan -ntal

research on weak interactions.

95

97

V. ACCELERATOR OPERATIONS

INTRODUCTION

This activity is concerned with operating the tandem-linacaccelerator system for nuclear-physics research. Before the summer of1977, the facility consisted of a 9-MV tandem Van de Graaff and its associ-

ated experimental system, which was operated continuously, seven days

a week. During a one-year period starting August 1977, normal operationis being interrupted frequently in order to carry out major technical

improvements designed to increase the capability for heavy-ion accelera -tion. During the fall of 1977, the tandem itself was greatly improved bythe installation of a new type of accelerator tube and by modernizing the

entire- vacuum system. Initial experience with the upgraded tandem indi-cates that the expected improved performance has been achieved. Thenext major task is the installation of a small superconducting linac to

serve ;is an energy booster for heavy ions from the tandem. Operation ofthe first linac section will start in mid-1978, and additional sections will

be added during 1979 and 1980, each such addition greatly inc reasing theresearch capacity of the facility. The accelerator will continue to be

operated for research during most of this period.

V

V. A1;298

A. TANDEM-LINAC ACCELERATOR

1. OPERATING EXPERIENCE FOR THE TANDEM

The FN tandem is one of the principal research facilities

of the Laboratory and for many years it was operated around the clock,

seven days a week, with certain exceptions. However, a reduced operating

schedule was initiated in Janua ry 1977 in order to free the manpower

required to prepare for the major upgrading that started in August 1977.

During the period 16 March 1977 to 31 December 1977 the

accelerator operated 2793 hours. Of this time, 75% was used for the6 7 . 1 12 13. 14 15 16 13 19~

acceleration of Li, Li, B3, C, 3, N, 5N, O, 0, , ,

35C1, and 63Cu ions, 9% for the acceleration of light ions (mostly le)

and 16% (455 hours) for machine development, testing, and conditioning.

The machine was not available for experimental programs from 8 August

1977 to 8 December 1977, during which time a major upgrading of the tan-

dern was carried out.

2. OPERATING PLANS FOR THE LINAC

The first use of the superconducting linac is planned for

the summer of 1978. Initially the operation of the new machine will be

aimed mainly at a study of the acc elf rator itself, and hence the operation

will be car ried out mainly by the staff members involved in its design.

Gradually, over a period of about a year, the operators of the tandem will

assume much of the responsibility for operation and maintenance. During

this same time the motivation for operating the machine will shift from

accelerator development to heavy-ion resva rch.

V. A3 99

3. UPGRADING OF THE TANDEM

During the first week of December 1977 the upgraded I Ntandem passed its acceptance tests with excellent performance l , exce((lingspecifications in several respects.

The upgrading project had as its objective to improve the

heavy-ion acceleration capabilities of the tandin. To this end, a high-

vacuum accelerator tube was installed, all vacuum components wcre

replaced, a new high-voltage (150 kV) terminal for the ion source W s

constructed and installed, and the optics of the lov-energy system wt

completely revised.

The most risky element of this upgrading was I' n ai< < le r -

ator tube. The inclined-field HVEC tube was replaced with on' inst uifac -tured by NEC. The NEC tube is a straight one with cylindrically-synimetricoptics. Our tube incorporates a new feature, permanent magnets placed

in the dead sec tions to suppress high-energy electrons. While the optics

of this tube are excellent and should allow for very good transmission,there was some uncertainty because of the electron-loading problems

expe rienced at Canberra and breakdown problems at Munich and at Tsukuba.

Because of differences from the modulus of the IIVIEC colun, the new

accelerator tube required its own voltage -distribution corona system.

The vacuum upgrading w;,s comnpletely successful (seeFig. 3.); the measured pressure is n.w -10-8 Torr, about three orders

of magnitude better than befr m.. I'he voltage carrying capability of the

accelerator tube seems much as before; it conditioned during the acceptance etests to a ~ve ) MV, and there is no obvious barrit r to gong somewhat

higher r.

The main purpose of the upgrading was to outi improved

heavy-ion acceleration. This purpose has been achieved: currents (some-

what higher than acceptance tests call for) of the ions 11, 160, 3nd 'Clhave all been accelerated through the tandem with a t ra nsni s sion 75,a factor of two higher than required in the acceptance tests.

No loading current was observed for oxygen beanims, and asmall loading observed when 2 A of chlorine is injected into the machinecannot be definitely attributed to electron loading; in any case, it dues ntconstitute a significant limitation. Now the main problem in act cl rating

intense heavy-ion beams is the short lifetime of the stripper foils.

To summarize, the FN upgrading, completed on schedulein 4 months, has been very successful. Ours is thus the first major elec -trostatic accelerator in the U.S. to operate with the Herb-type (NFC)

V.A3100

.~ 1

U*

* JIJ

1WEd

37Sv

"'S A

"rt

Fig. 35. Pete Billquist (left) and V'at Den Hartog installing the

high-vacuum beam line at the low-energy end of the Tandem.

accelerator tubes, and the first ho ri:v(ntal tandem anywhere to use several

new NEC features such as magnetic electron traps and a separate corona

system for the accelerator tube. The whole project was carried out almost

entirely by the tandem-optration staff, with some assistance and advice

from NEC prsonnel.

The res(ar Ih pr,)gram at the tandem was resumed on

December 12 and will continue until late spring 1978, when the supercon-

ducting linac will be ready for beam tests. During 1978, it will be

necessary to interrupt the resta rch program periouacally for short inter-

vals in order to complete a nurnbter of tasks associated with the upgrading.

Additional details concerning pa rticular facets of theupgrading are given below.

I

'u

V. A3a, b

a. Tandem -Injection System

The injection system allows the use of three source positions.

The center position is used for the Li-exchange duoplasnatron, which

produces 40-keV lie beams. The west position is occupied b dire( t-

extraction duoplasmatron and a Penning source, which produce bams with

an energy of 35 keV. The east position is occupied by the inverted sputtbfr

source,.

Since the sputter source in the east position will be the maiin

source used with the superconducting linac, the enti re be;tinm Ime ;Is wic

with it has been redesigned and rebuilt. Major charges are as.-Is fl uw:,.

(1) The injection voltage was increased to 150 kV and the highly -stable pev r

supplies required for beam bunching were provided. (2) The n;ss -energy

product of the inflection magnet was increased to 20 by replacing the coil.

(3) The vacuum system was upgraded. (4) A va riable beam atteniuator was

installed. (5) The beam-optics system was modified so as to rm;itc h tih

beam to the requirements of the new ac< ele rator tube and so as to provide

good mass resolution.

u. High-Energy and Low -Energy Beam Lines

The beam lines were replaced entirely by an all metal-

cerarnic system in order to obtain a satisfactory operating vacuum fur th,

accelerator tubes and avoid contamination of the tubes. The haiked low -

energy and high-energy lines operate at a pressure of about 10 Torr.

Although this pressure is quite low, we are concerned about the possibility

that old turbomolecular pumps still in the beam lines might in time

contaminate the accelerator tube. To avoid this, the turbopumps will be

replaced by cryogenic pumps.

The low-energy line contains an electrostatic quadrupole-

triplet lens, which is the focusing element used for beams injected at 150 kV.

To permit adequate transmission of beams injected at a lower energy

101

V. A3b,c;4a

(,40 keV), a 2. 5-in. einzel lens is located as close to the base of the

accelerator tank as possible.

c. Tandem Terminal and Terminal Control

The original terminal vacuum box has been replaced by a

new high-vacuum box. This box is a temporary one in which only foil

stripping is possible. A more complete system that permits gas stripping

will be installed in the next year.

Developmental work on a system to control components in

the terminal is in progress. A microprocessor linked by a single fiber-

optics cable to a light-emitting diode has been tested and appears to be a

promising control system. Surge protection for the microprocessor was

adequate during normal operation of the tandem, but the rotection was not

adequate during a period of machine conditioning, when the accelerator tube

frequently sparked to ground. An alternative control system that uses an

independent light link for each control function is also under construction.

4. OTHER DEVELOPMENTAL ACTIVITIES

a. Beam-Bunching System

The picosecond beam-bunching system for heavy ions going

into the West Target Room was completed and successfully tested before

the tandem shut down in August. This system is designed to be a useful

research tool in its own right and it is also the prototype of the buncher

system for the linac.

The new bunching system consists of (1) a pre-tandem

normally-conducting buncher, (2) a post-tandem superconducting buncher,

(3) a bunch-phase detector that dynamically links the two bunchers, and

(4) a post-tandem chopper, these components operating at 46, 92, 92, and 23

MHz, respectively. The pre-tand m butcher consists of a single

102

V. A4a,b

acceleration gap with aligned grids and is excited by an rf voltage with a

sawtooth waveform. Time-of-flight measurements yielded pulses 0.6

and 0.9 ns wide (FWHM) for 1H and 12C beams, respectively, with over

75% of the dc beam compressed into the pulses. The post-tandem buncher

compressed the pulse further down to 50 ps (FWHM).

The successful operation of the full system demonstrated the

effectiveness of the bunching concept for operation with the superconducting

linac. The bunching system will now be used immediately to bunch tandem

beams required for the experimental program.

b. Foil Stripping

At the present time, only foil stripping is possible in the

tandem terminal. From most points of view, foil stripping is preferable

to gas stripping, but the use of foil stripping is probably limited to ions

with A ' 60 because of unacceptably short foil lifetimes. Consequently,

we intend to undertake the difficult task of installing a gas stripper in the

terminal and, in the meantime, various possible ways of extending the foil

lifetime are being investigated.

A 3-MeV heavy-ion beam (typically krypton) from the

Dynamitron is used to study foil lifetimes. The following approaches were

explored during the past year: foil heating, foil oscillation, the use of

different backings (including grids), and the use of different foil thicknesses.

Of these, only a combination of heating and oscillation extends the lifetime

by an important factor, about 6, and it is not clear that this factor is

large enough to warrant the complication involved in the design of a

practical device to heat and oscillate the foil.

Other experiments on foil lifetime are in the planning stage.

103

104

5. UNIVERSITY USE OF THE TANDEM ACCELERATOR

For the first two-thirds of 1977, before the shutdown for

upgrading, the Argonne FN tandem accelerator continued to be heavily

used for research by scientists from neighboring academic institutions.

Of the total time available for research, 43% was allocated to experiments

in which visiting investigators participated. In every instance the outside

user chose to collaborate with Argonne scientists. In addition to using the

tandem itself, outside users have continued to rely on various support

facilities associated with the tandem (such as the automatic plate scanner)

to process data acquired both at Argonne and elsewhere.

The Resident Graduate Student Program remained strong

during 1977. Under this program, predoctoral students in residence at

Argonne use the tandem to conduct experiments which serve as the basis

for doctoral theses. The work is carried out under the joint direction of

a local staff nEnbe r and an advisor from the parent university. During

1977, student mrembers of the program pa rticipated in experiments (directly

related to their theses) that used 49% of the total time available for research.

A list of institutions from which visiting scientists came in

1977 follows. Included in the list are the names of Argonne collaborators,

enclosed in parentheses, and the titles of the research done.

(1) Beloit CollegeFocal - Plane - Detector Development

J. C. Stoltzfus and (J. R. Erskine)

(2) University of Kansas 15

Fusion of Heavy Ions Induk td by NF. W. Prosser, Jr., (D. G. Kovar, and S. L. Tabor)

Fusion of Oxygen and Magnesium IsotopesF. W. Prosser, Jr., (D. F. Geesaman, W. I lenning, D. G.Kovar, K. E. Rehm, and S. L. Tabor)

(3) University of MichiganDetermination of Hydrogen Depth Profiles Using Heavy Ions

A. Hanson, (M. J. Murphy, and E. B. Norman)

V. A5

V.A5

(4) Michigan State University

Search for a AT=1 Parity -Violating Hadronic Interaction

R. G. H. Robertson, R. A. Warner, (T. J. Bowles, and

R. J. Holt)

(5) Northern Illinois UniversityCoulomb Excitation of Nuclei by Energetic Heavy Ions

D. L. Bushnell, (I. Ahmad,t A. M. Friedman,t andR. K. Smither)

High-Spin States Induced by Energetic Heavy Ions on NucleiD. L. Bushnell, (I. Ahmad,t A. M. Friedman,t andR. K. Smither)

(6) Northwestern University

Giant Resonances in 9 0 Zr Induced by Alpha Capture in 86Sr

L. L. Rutledge, Jr., (L. Meyer-Schutzmeister, K.

Raghunathan, and R. E. Segel)

(7) University of Pittsburgh

Fusion of Heavy Ions

J. V. Maher, (D. F. Geesaman, W. Henning, D. G. Kovar,and K. E. Rehm)

(8) Purdue University

Gyromagnetic Ratios of High-Spin StatesT. V. Ragland, R. P. Scharenberg, and (R. E. Holland)

(9) Western Michigan University

States of '1 5 V Excited by 6 Li on ' 0 CaG. Hardie, (: . J. Elwyn, S. A. Gronemeyer, L. Meyer-Schitzmeister, and K. E. Rehm)

Lifetime of a 3/2 State in 43TiG. Hardie, (A. J. Elwyn, S. A. Gronemeyer, R. E. Holland,L. Meyer-Schutzmeister, and K. E. Rehm)

The following is a list of students participating in the

Resident Graduate Student Program who did research at the tandem during

the past year, their home universities, and their local advisors. Those

who received their doctoral degrees during the year are indicated by an

asterisk.

(t) K. Daneshvar - University of Illinois-Chicago Circle CampusD. G. Kovar, adv.

(2) S. A. Gronemeyer - Washington University

L. Meyer-Schutzmeister, adv.

- DChemistry Division, ANL.

105

106 V.A5

(3) M. J. Murphy - University of ChicagoC. N. Davids, adv.

(4) E. B. Norman - University of Chicago

C. N. Davids, adv.

(5) K. Raghunathan* - Northwestern Univcrsity

R. E. Segel, Idv.

(6) T. R. Renner - University of Chicago

J. P. Schiffer, adv.

V. Bi

B. DYNAMITRON OPERATIONS

The Physics Division operates a high-current 4. 5 -,1VDynamitron accelerator which has unique capability as a -onrce of ioni'; d

beams of most atoms and many molecules. Among the unusual f-wilitiasassociated with the Dynamitron are (1) a beam line c pi btl of providing

"supercollimated" ion beams permitting angular measuremrniits to

accuracies of 0.005 degree, (2) a beam-foil mea suir emetnt system capableof measuring lifetimes of a few picoseconds, (3) an experimental system

dedicated to measuring absolute nuclear cross sections at low energy,(4) a precise angular-correlation system for wea k-interaction studies,and (5) a simultaneous irradiation system by which heavy ions from the

Dynamitron and helium ions from a 2-MV Van dt Graaff accelerator a refocused on the same target. An advanced PDP-11/45 cornmiter system is

used for on-line data analysis and for the control of expi rimental syst Ins.

The Dynamitron c ontinues to develop as a facility for txpe ri -

mental research. In 1978 a new Penning-type ion-source and an rf ion

source .ill be brought into operation. Also a hot-filament source employing3-eucryptite will be used to produce beams of lithium and lithium hydridesfor use in both the beam-foil spectroscopy and the molecular-ion p rogram s.

These sources in conjunction with the existing Duoplasmatron source c will

permit the acceleration of a great variety of beam spf-cies (including some

multiply-charged ions). The accelerator facility is presently well equippedwith an on-line computer for the control of experiments and for on-line

data acquisition and analysis. In thi next two years we plan to extend the

use of computers to the monitoring and control of the accelerator itself.

This will be done uing microcomputers. Control and readout of ion-source ,aram trs will 1 c .mplem ented using a light -beam link to the high-

volt;ge terminal of the accelerator. Microcomputers will be used in

other routine tasks -e. g. , the running of magnet scans to determine themasses of the various ion beams emerging from the accelerator.

1. OPERATIONAL EXPERIENCE

F. P. Mooring, D. S. Gemmell, A. Langsdorf, Jr., and R. L. Amrein

During the past year, the Dynamitron has run exceptionally

well. The machine was staffed for a total of 6615 hours of which 5685 hours

were scheduled for experiments and 930 hours were used for upgrading the

system and interchanging ion sources and ion-source gases. During the

107

V.B1

time the accelerator was scheduled for experiments, an ion beam was

available for use 86% of the time.

A wide variety of experiments was performed during the

year requiring many different ion beams and a large range of experimental

conditions. Ion currents on target from as low as a few nanoamps to more

than 100 A were used, while ion energies ranged from below 200 keV to

1 +4 MeV. Among the atomic-ion beams used by experimenters were H1,2 + 4 + 12 + 14 + 16 + 20 + 35 + 37 + 40 + 51 +

11, Iie , C , N , 0 , Ne , Cl, C1 , A , V ,

58 I+ 6 0Ni+, and 4Kr+. A large number of experiments utilizing

molecula r ions were also performed. Among the molecular ions used

were all of the various hydrogen molecular ions, as well as the helium -

hydrogen molecular ions, and (12 C- 1 ) , (12 c - 1) , (12 C -6

14 1I + 14 14 + 16 1 + 16 1 + 16 1 + 20 1 +(N- 13) , (N-N) (0-11), ( -H (0 3)(Ne-3H),

and (4 0A r-1-1)+.

The new tube installed in October 1976, and reported upon

last yea r, has continued to perform as it did when first installed, without

any indication of either gradual or sudden deterioration. The thus far

appa rent success in use of this tube lends encouragement to the opinion

that the unique new design for decoupler diaphragms used in it and briefly

described last year, has features that may usefully be refined and exploited

in succeeding generations of acceleration tubes in various dc accelerators.

At the end of calendar year 1976, the vacuum tube diodes in

the Dynamitron were all replaced with solid-state diodes. The revised

charging system has worked well and besides reducing the chance for a

serious and costly accident has improved the operation of the accelerator.

The lower limit for the terminal voltage i- now determined by the optical

characteristics of the ion-source system rather than by the charging system.

Terminal voltages as low as 200 kV are now routinely used by experimental -

ists.

No solid-state diode assembly has failea to perform, though

one or two individual diodes in several assemblies have opened. However,

108

V. B1

such failures (Io not affect the operation of the accelerator and it is only

by testing each of the hundreds of individual diodes that such failures

have been detected. Thus the likelihood that an open diode assembly will

initiate a damaging power arc has been reduced to almost rt.

The vacuum manifold at the exit of the w-t( hing mbLnt

was dismantled and inspected for beam damage town rd the end -f 197?.

No visible damna ge has occurred during the period that the Dyna n citron has

been in operation. Fears that the large beams us ed during this period

had eroded the beam stops within the manifold proved grouiondltess. While

the manifold was disassembled, it was cleaned thoroughly. -Pitnr to tht

dismantling, the oil diffusion pumps had been rcpla ced with tui-rbomolet cla r

pumps.

The power supply for the switch hing ma gnet was replaced

with one that is more stable. Thce mgnctic field is now constant to (0.Ott

gauss at 4550 gauss, 0. 5 gauss at 8200 gauss, and 0. 1 gauss at 9000

gauss. The improved stability allows precision mta suremtnnts to be iiad,

that could not be done formerly.

The radiation-safety and intt rlock systein has been upgrade d

to the point that it can now b- u5ed routinely. Formerly, line surges

introduced signals into the logic circuit that would shut down operations.

A long and intensive study of the system finally revealed the source of the

spurious signals, and proper filter circuits and the nee essary rf grounds

were incorporated. The system now works well.

Because of the experimental demand, the new terminal his

not yet been installed. The terminal, which is designed to minimize down

time and increase operational efficiency will be installed during the first

half of the new year.

A new ion-source system designed to yield multiply -cha rgcd

ions as well as a large range of metallic ions has been purchased from a

commercial supplier. Delivery is scheduled for March 1978. The system

incorporates a PIG ion source, an extraction system, an einzel lens, a

I ()9

V. B1;2

mass selector, 'Ind a matching lens for the accelerator. The source is

3,4 ++ 20 +++gua ranteed to (elive r 3 A of He , 1.5 A of Ne , and 4 1,,A of40 +++

Ar . It will be installed during the summer of 1978.

As many as 56 scientists supported by various technical

personnel performed experiments at the Dynamitron during the past year.

These investigators came from three Argonne research divisions, six

American universities, ind one foreign research institute. Also included

were three students enrolled in Argonne's P esident Graduate Student Pro-

gram working under the direction of local Physics Division staff members.

Within Argonne, twenty-six chief investigators came from the Physics

Division, fifteen from the Materials Science Division, and three from the

Solid State Scienc( Division. 1levn visitors came s outside users from

American universities, a;nd one from an Israeli institute.

2. UNIV lRSITY US! OF TE. DYNAMITRON

F. P. Mooring, D. S. Gemmell, and R. L. Am rein

E"ach group of outside users (with one exception) chose to

collaborate with Argonne scientists in their research performed at the

[ynamitron. Of the total scheduled time, 27% was allocated to experiments

performed with outside users pa rticipating. A list of the institutions

represented is given below with the title of the research done and the names

of the principal investigators. The names of the local collaborators are

enclosed in parentheses.

(1) University of ChicagoAtomic Excitation by Heavy -Ion Bom ba rdment

1. DeSerio, T. J. Gay, (H. G. Berry, G. Gabrielse, andA. E. Livingston)

(2) Marquette UniversityRadiation Damage Studies of Covalent Crystal Structures

L. Cartz, R. Fournelle, C. Ma, and S. R. Srinivasa

110

V.2

(3) Middlebury CollegeThe Behavior of Molecular Ions Passing Through Matter

P. J. Cooney, (D. S. Gemmell, W. Pietsch, A. J.Ratkowski, and B. J. Zabransky)

(4) Northwestern University

Testing and Development of a Nal Spec trometer

C. Chen, R. El. S gel, and (T. J. Bowles)

(5) Princeton UniversityParity Violation in 10B

C. Gagliardi, (I. J. Bowles, G. T. Garvey, ;nd H. ).NI (Keown)

(6) Stinford University

Pa rity Violation in B

S. J. Freedman, (T. J. Bowles, G. T. G; rvey, ;Ij(d R. 1).

Mk Keown)

(7) Weizmann InstituteThe Behavior of Mole( ult r Ions Passing Through Matter

Z. Vage r, (I). S. Gemrnel , W. 1'ietsch, A. J. Ratkowski,;fnd B. J. Zabransky)

The students participating in the Resident GraduAte Student

Program, their home institution, and their local advisor are listed below.

(1) C. Gagliardi - Princeton University

G. T. GIa rvey, adv.

(2) G. Gabrielse- - University of Chicago1. !. 'e rry, adv.

(3) !l. I). M Keown - Princeton UniversityG. 'I. Ga rvey, adv.

These students participated in experiments which used 31% of the scheduled

time.

fit

VI

VI. NEUTRON PHYSICS

INTRODUCTION

Neutron research in the Physics I)ivi siun at A rgonne his

been devoted almost exclusively to experiments which take advanta gc of

unique capabilities of the Argonne threshold -photoneutron facility. In this

type of study high-resolution (y,n) reactions are viewed as invt rs neutron-

capture reactions and the radiative transitions are the probes uistd in the

spectroscopy of excited nuclear states. The importance of the techniwie

lies in its ability to reach regions of excitation in nuclei which are i( ;css -

ible by other more traditional neutron-induced reactions and with aresolution and sensitivity which is unexcelled. While threshold photo-

neutron experiments have provided much new data on probl ms of topical

interest in neutron physics, the technique also has proven itself in studies

of basic problems in nuclear physics such as the question of the existenceof giant magnetic dipole resonances.

Traditionally, the A rgonne neutron-physics prog r;. inc luded

a vigorous program of measurements of fundamental properties of the

neutron. Such data have re-emerged in importance recently with the

intense interest in gauge theories of fundamental ntc reactions of elenmo-nta, ry

pa rticles. A careful determination of the electric -dipole moment of the

neutron or a correspondingly precise upper limit would provide a critical

test of the most successful of these, the Weinberg-Salam theory. The

prospect of an intens, pulsed neutron source at A rgonne offers new possi -

bilities in this area, and an ANI.-University collaboration has begun

development of an ultracold-neutron facility with the objet tive of m;+ snasure-

mc'nt of the dipole moment, of the requisite accuracy. If prelirnar

ce sign estimates are correct, the technique planned should ,>rOvide ti'

most sensitive measurement in its class.

A third element of the neutron program has been a srmialleffort d:-voted to final analysis of spectroscopic nuclear data gathered

prior to the shutdown of nuclear research at CP-5. This work will 1e

completed in the next six months. The data are proving to be very inpor-

tant to current discussion of nuclear models for the level structure of

transitional and deformed nuclei.

113

VI. A

A. iII i- N LI.) L PHOION EU IU ON STUDIES

Ihe photonh( lea r program is designed to take advantagt- of

the caability of the Argonno electron linac to furnish very intense ben rn sof pulsed brersstrahlung with excellent tine and energy resolution for

photon energies in the range of 5-20 MeV. These conditions are idealfor the stdy of photone it ron spectra in the threshold region, and the (y, n)

re;.ction ha s been utilized as a powerful tool for thm spectroscopy of highly-excl'ed indivi 1ual niicle;ir staht s. An obje< tive cornon to many of theseiea-urements is the determine tion of the spin and parity a ssignments of

resonanet-s obs er v -d in the photoneutron spectrum. One a dvantage of thethreshold-photon( utrun technique is the eas(e with vhich such data can beobtained by measurements of photoneutron angula r dist ributions andpoly rizations. The AN L pola rin - ter for neutron-polarization studies hasbeen a major clernnt in recent experiments. A large nurnb er of definitiveassignments made in ANL measurements have contributed to our under-

standing of current topical problems in nuclear structure such as the searchfor giant magneti( -dipole resonances.

In addition, the (y, n) reaction is an attractive pro:b, ofreaction mechanisms for neutron reactions It is a -;ingle-channel. reaction

in both entrance and exit channels. The cross section (an be analyzeddirectly by means of widely recogniz(-d re .c tion theories. Unlike neUtron-induced reactions, measiuremrnts of r-idiative transitions in individuo;lresonances can be extended well ite, 1 MV rantv. Analysis ofphotoneutron-reaction data for P nuclei provides fine ;namplE-s of normal

compound radiative transitions, n(onresonant direct c(ipture, and so-called

exter na l -channel capture (resonant c-:a ptu rc out side the nudeIa r surface).The recent data on 17() provide the first direct observation of the interplay

of such internal- and external-channel capture processes.

Two fac ilit- irproveinents which should inc rea se the

sensitivity and r solution oX the Argonne experiments are in progress.

A new xiltidi rectional beam -transport system that will provide the capability

of measurements over the full range of photoneutron production angles isunder construction. P)rescently nmt :surements are limited to 00 . 9 K 1800.In addition, the new system will have ri vertical mode of operation whichwill make possible direct precision calibration of beam lines in angulardistribution measurement. This is an essential feature of the plans to

study the photodisintegration of the deuteron. In addition the 90 and 1350flight lines are being lengthened to accommodate neutron drift paths of up

to 25 m.

1 14

VI. Aa

a. Photodisintegration of the Deuteron

i. E. Jackson, R. J. Holt, and R. M. Laszewski

The deuteron is the sirnplest nuclear r s stvm for testing

various Models of the nucleon-nucleon interaction. It is of ;, rti cuiia r

interest because it is the one system for which the fftcts m (son

exchange currents and virtual isobar states can be calculated accurately.

The photodisintegration of the deuteron is a particularly attractive re 'Cition'i

for probing the tw o -nucleon system since the basic inte raction is u e o U t elr

understood. Until rec ently, it was generally acc (pt('d that the I)(y,)

reaction at mrod(erate proton energies was understo wi «with ge ()d pr cisi n

in terms of potentials which have been determined f rom fits to twA -nucleon

scattering data when corrections were applied for meson exchange currents.

However , recent new measurements at Mainz of thc D(y, n) reaction at

t8(0 have shown a startlingly large -20 to 40 per( ent-discrenancy with

all reasonable theoretical estimates of the photodisinti gration -im lplittide.

I'heV highlight the importance of careful and comprehensive measurement s

of photoneutron angular distributions and polarizations over the r< gi- ln from

threshold to 20 M(V. The existing data base is surprisingly limited.

Initial mn easu rem ents at the ANL facility have focused on

a determination of the angular distribution in the thresh old re ion wh-re

the amiplitu de is par ticularly sensitive to mcsonic efIec ts. A pr (isiun ul

about 10% has been achieved, which is adequate to test the simple< ( ff tive

range theory. To date measurements have been limited to observation It

900, 1350, and 1550. It was evident from the data that a substantial

improvement in precision would be possible only with measurements

over the full angular range of photoneutron angles and with a direct means

of calibrating the relative detection efficiency at each angle. To that end,

a multidirectional photoneutron transport system is under construction.

This system will provide bremsstrahlung beams on demand vertically for

efficiency calibrations and horizontally in modes corresponding to angles

of observation along our photoneutron flight lines in either the furwrd

115

VI.Aa-c

and backward hemisphere. The system should be completed about June

1978. More precise determination of photoneutron angular distributions

over the full range of angles will facilitate our search for interference

effects which art. a signature of possible final-state interactions or

momentum-dependent components in the nucleon potential. We also intend

to extend our measurements to higher photon energies to probe the anomalies

reported in the Mainz measurements.

b. Ground--State Photoneutron An gular Distributions for Excitations

Between 6.3 and 9.3 MeV in 13C

R. M. Laszewski, R. J. Holt, H. E. Jackson, Jr. , and J. R. Specht

There are several proposed effective interactions that have

been able to fit the energy -level structure of p-shell nuclei reasonably well.

A partic ularly good test of the wave functions that are obtained from the

diagonalization of a model Hamiltonian is to compare the computed strengths

for photon decay to the ground state with measured radiation widths where

they are available. We have made very high-resolution measurements of

the 13C(y,n)12C ground-state photoneutron cross section aT laboratory

angles of 900 and 1350 and for excitations up to 9. 3 MeV. The data are

being analyzed using the R -matrix formalism to obtain ground-state

radiation widths for resonances at 7. 5, 7.7, 8. 3, and 8.8 MeV. In'

addition to these resonances, we are able to observe the nonresonant

contribution to the photoneutron cross section directly.

c. Effects of Radiative Channel ,.id Potential Ca pture in the 17(,n )i60Rea ction

R. J. Holt, H. E. Jackson, R. M. Laszewski, J. E. Monahan, andJ. R. Specht

The differential cross section for the 17O(y, n )160 reaction

was observed with high resolution throughout the photon energy range

4. 5-7. 0 MeV and at angles of 900 and 1350. The Argonne high-current

electron accelerator was operated in the unique "pico pulse" mode (pulse

116

VI. Ac 117

PH CTCN ENERGY Vwidth: 35 ps, peak current: 200 A, 4.2 4C WE . ..

pulse rate: 800 H ) in order to 0.12- Oin )z

obtain optimum resolution from

the time-of-flight spectrometer.

The observed cross sections are

shown in Fig. 36. The interesting

features of the spectra are: (1) II,

a nov'el interference pattern in the ,

form of a symmetric minimum at ) h4)r\ r

5. 38 MeV, (2) the first directly 4

observed nonresonant cross sec -

tion in a photoneutrun reaction,

and (3) the best example of a

single-particle M spin-flip tran-

sition at 5. 08 MeV. The results

were interpreted in terms of the

theory of radiative capture of

Lane and Lynn. We discoveredo I.

the first unambiguous effects of N JTRON ENEG .Me

radiative channel capture in aFig. 36. The points depict the ob-

photonuclea r reaction. It was served angular distribution for the

found that a channel capture 1 7 0(y, no )160 reaction, while the

curves represent the results of the

resonance can manifest itself as multilevel, self-consistent R -matrix

a symmetric minimum in the (y,n) analysis.

cross section, whereas -a reson-

ance that arises from internal capture cannot. A symmetric minimum in

170 occurs at the location of the 5. 38-MeV, El resonance as shown in

Fig. 36. In addition, the large nonresonant cross section in the17 16

O(yn) 0 reaction was interpreted as potential capture; consequently,

this reaction represents an ideal example of the Lane-Lynn theory of

1A. M. Lane and J. E. Lynn, Nucl. Phys. 17, 563 (1960).

118 VI. Ac,d

radiative capture. In order to account simultaneously for both the neutron

and photon channel in 170, the realistic neutron scattering wave function

was used to represent the i60 + n system outside a channel radius. This

wave function was introduced in a self-consistent way using the Yale

R-matrix parameters for the elastic neutron channel. The final self-

consistent R-matrix analysis is represented by the curve in Fig. 36.

2G. T. Hickey, F. W. K. Firk, R. J. Holt, and R. Nath, Nucl. Phys.

A225, 470 (1974).

d. Doorway States in 29Si(n)

H. E. Jackson, R. J. Holt, and R. M. Laszewski

29In a recent study of the reaction 29Si(y,n) near threshold,

we found evidence for a doorway state with J = common to the channels

28 29Si + n and Si + y near E = 750 keV. Subsequent theoretical calculationsn

supported this interpretation and reproduced the neutroA and -y widths with

reasonable precision. These calculations predict the existence of additional

doorway structures at higher neutron energies. We have extended our

measurements to higher neutron energies using the ANL picosecond

photoneutron source in an effort to search for these states. Preliminary

results suggest the existence of a localization of strength near 1.7 MeV of

the type predicted by the particle-vibration model of Halderson et al., but

the location and strength do not appear to be consistent with their

29S (y,n) p = 0.64Io-

5-

Fig. 37. Ground-state radiationC-- - widths I' and reduced

20 neutron widths yn forresonances with JTr = z in

40 the 2 9 Si compound nucleus.

0 0.5 1.0 1.5En (MeV)

VI. Ad, e

calculations. The results of a correlation analysis of the ground -state

radiation widths and reduced neutron widths for resonances in 29Si are

shown in Fig. 37. Observations at higher excitation energies where thi,

model predicts additional concentrations of reaction strength will provide

a definitive test of the model. Such high-resolution measurements are

planned using new 25-meter neutron flight paths currently under construc-

tion.

119)e. Search for the Giant Magnetic Dipole Resonance in Sn

R. J. Holt, R. M. Laszewski, H. F. Jackson, Jr., and J. R. Specht

A search is being conducted for collective proton spin-flip

transitions in the 119Sn nucleus. The Harwell photoneutron group suggested

that the broad resonance structure (~400 keV wide) at in excitation energy

of approximately 7. 8 MeV in W Sn is due to a collective M I excitation.

One would expect that a resonance of this nultipolarity would produce a

polarization in the emitted photoneutron beam at a reaction angle of 900.

Last year the photoneutron polarization at 90 was found to be zero, within

statistical error limits, throughout the energy range 7.4 to 7.9 MeV.

These data gave the first indication that a collective Ml resonance is not

present in this energy range in 119Sn. However, one might argue that the

level density in this energy range is so high that polarization effects might

be averaged to zero. As a test of the sensitivity of the polarization method,0

the photoneutron polarization was observed at a reaction angle of 135 .

At this angle one expects El excitations to give rise to a photoneutron

polarization effect. Indeed, a nonvanishing polarization was observed at

1350. On the basis of these data, efforts are underway to establish an

upper limit on the Ml strength in this energy region.

I t9

VI. Af

f. The Collective M1 Resonance in 208Pb

R. N'. Laszewski, P. J. Holt, and H. E. Jackson

208Because there are a large number of rtcleons in Pb

which -an undergo spin-flip transitions, this nucleus is thought to be an

ideal one in which to study the collective MI resonance. I early (y, n)

angular distribution experiments done at Livermore had suggested that

seven strong resonances spread over 700 keV of excitation centered at

7. 9 MeV could account for most of the expected theoretical M I strength,

although no theory could rea dily explain this amount of fra gm entation.

For excitation between 7. 5 and 10 MuV, we have observed the polarization

of photoneutrons from 208Pb as well as measured their angular distributions

with very high resolution in a series of experiments in order to investigate

in detail the distribution of MI strength in this nucleus. It w.a s found that

of the original seven resonances thought to be MI, only one, that near

8 MeV, could be consistent with a 1 assignment on the basis of the

polarization data. A number of resonances were found to have an unexpected-

ly large s-d wave admixture in the outgoing neutron channel which would

explain their misassignment on the basis of angular distributions alone in

the Livermore experiment. We have also found some evidence for a number

of unexpected small M1 resonances above 8 MeV which together may amount

to a significant fraction of the MI sum rule. A theoretical treatment of

the problem by Dehesa, Spt ''i, and Faessler which includes two-particle

and two-hole configurations has been able to describe qualitatively our

observed distribution of i resonances.

Recently, Oak Ridge has reported the observation of many

additional weak M1 resoinanc-s between 7.4 and 7. 7 MeV using a combina-

tion of (n,n) and (n, y) measurements. Their reported strengths, however,

tend to be a factor of two larger than our (y,n) work would allow.

1S. Raman, M. Mizumoto, and R. L. Macklin, Phys. Rev. Lett. 39,598 (1977).

1 20

VI. Af--h

With the extended time-of-flight tunnels that are now available

to us, we are in the process of calibrating our transition strength measure-

ments directly to the deuteron cross section, and refining our energy scale

so that direct comparison with the high-resolution (n,n') dati will be possi-

ble. This last is very important because the neutron scattering experiments

-ire sensitive to resonances of many more multipolarities than a re photo-

neutron measurements. It is difficult at present to be certain whether r or not

the same resonances are being compared, or to establish whether a given

resonance in the neutron data is present at all in the photon channel.

g. Calculation of Differential Polarization Coefficients for (L Y 1't rticl()

Reacti 'ns

R. M. La szewski and R. J. H1olt

Both angular distribution and differential polarization m eas-

urements a re important for an understanding of the nuclear-structure

impli ;ttions of states involved in photonuclear relations. There are

convenient compilations of angular distribution coefficients which fa litate

the analysis of differential cross-section data. It i5 only recently,

however, that expe rinental techniques for the measurement of particle

polarizations have been developed, at this laboratory a::d at other labora-

tories, to the point where a similar compilation of differential polarization

coefficients has become desirable. We have generated tales of differential

polarization coefficients for endtted particles of spin 1 and for target and

residual nuclei with spins 5. The tables cover Ei, M1, and 12 radiations

and their various interfering combinations in the entrance channel.

h. Studies of the 12C + n and Li + n Systems Below 4 MeV

R. J. Holt, P. T. Guenther,. A. B. Smith,* and J. F. Whalen*

Because of the overlap of the analysis techniques, there are

frequently areas of mutual interest to the photoneutron program and related

Applied Physics Division, ANL.

121

VI. Ah

applied programs at Argonne. This work was performed in collaboration

with the Applied Physics Division. Precision measurements of neutron

elastic scattering from t2C and Li were performed between 1.5 and 4.0

MeV using the Argonne Fast Neutron Generator. Measurements of this

precision should prove valuable for nuclear-structure information, the

proposed Li blanket in fusion-powered reactor designs, reactor applica-

tions and convenient standards for experimental studies of neutron-induced

processes. A multilevel R -matrix analysis, which includes considerations

of previously reported observations of cross sections and polarizations,

of the new 12C: angular distributions is inI progress. This work represents

the first systematic study of the Li + n system in the MeV region. No

definitive resonanmcr( structures appear to be present between 1.'; and

4. 0 MeV. A multilevel, rnmltich;mnel R -matrix code will be developed in

order to study the Li + n system in the MeV range.

1 22

VI.B

B. MEASUREMENT OF THE ELECTRIC DIPOLE MOMENT

OF THE NEUTRON

V. E. Krohn, G. R. Ringo, J. M. Carpenter, T. O. Brun,T. W. Dombeck,t J. W. Lvnnt and S. A. Werner"

The object of this project is to measure the electric dipole

moment (IEDM) of the neutron using stored ultracold neutrons. The EDM

of the neutron, because it can be measured with such great sensitivity,

has provided a useful challenge to fundamental-particle theories. It has

been instrumental in disposing of about 15 of these and at the moment is

on the edge of testing the very successful Weinberg-Salam gauge theory of

the weak interaction. In the currently popular model, which gives CP

-24 1nonconservation, the EDM is calculated at 1.6 ' 10 cm. The present

-24 2measurements give an upper limit of about 3 >' 10 cm.

The sensitivity of the measurement to the length of time

neutrons spend in the measuring apparatus makes the use of ultracold

neutrons (UCN) stored in containers an attractive possibility for this

measurement. These neutrons have velocities lower than 7 m/s and are

totally reflected at All angles by the container walls. They can be measured

for 100 seconds or more. By using a shutter on the container, opened

only when the source is on, a pulsed source of UCN can give as large a

number of stored neutrons as a steady state source with a flux equal to

the peak flux of the pulsed source. Argonne has such a source in the

ZING-P' project and calculations suggest it will give a higher density of

UCN in a container than can the high-flux reactor at Grenoble where another

EDM measurement is planned.

Solid State Science Division, ANL.

tUniversity of Maryland, College Park, Maryland.

University of Missouri, Columbia, Missouri.

S. Weinberg, Phys. Rev. Lett. 37, 657 (1976).

2 W. B. Dress et al., Phys. Rev. D 15, 9 (1977).

123

VI. B

At Argonne the UCN will be

/ . di JJ produced by reflection of 400 rn / s neutrons

P1l from ZING-P' by a mica crystal on a 200 rn/s

rotor synchronized to the (30/s) pulses from

T the source . The UCN will be stored in .

bottle which will be placed in a combined

- -- ma gnetic and electric field and the precessiOn

rate measured with the electric field parallelINr, G.

;11nd a ntiparallel to the magn (tic. The

apparatus for the production a;nd storage of

Fig. 38. Apparatus for UCN (Fig. 38) is under construction.

the production and If a d ns ity of mo)re than 3storage of ultra coldneutrons. UJCN/cc can be a(chieved, and it 5ppea rs

quite possible, the accuracy of the EIDM-24

measurement could be improved from the present 3 10 c m to about

1 / 10-25 (1. In all probability this will however require the further

suppression of some significant sources of systematic errors below the

levels that were tolerable in the exisLing measurements (e . g., lcakag(

currents from the electric field plates).

There is a good possibility that the UCN facility will be

useful in studies of neutron-surfalce intera c tions and perhaps in such

fundamental studies as neutron lifetime measurements and observation

of macroscopic quantum effects.

If the much better IPNS pulsed source becomes available,

a really superlative E'DM experiment will become possiblV.

124

VI. Ca

(. NUCLEAR STRUCTURE STUDIES WITH NIVUJTRONS

Although nuclear measurements at the CP-5 reactor wre

terminated in July 1976, analysis of data generated in this program has

continued. An extensive and very valuable body of nvut ron ca ptur spectra

has been gathe red. Detailed reduction and interpretation of this dat;z is

providing useful insights into a number of questions of g reat current int< rest

to our understanding of nuclear level structure. The objective of this work

has been to compare level scheme systernatics and '-ray branching riosystematic s, in order to distinguish between the many nuclear r theories

which might appl . The profusion of models makes it important thatdata be a s comnpl te as possible. A substantial effort has been made tt

identify all low-spin levels (J 6) and a l.l EI, 1:2, andi M i transitions

am>ng levels below 3-MeV excitation. Data analysis is nearing t om pleti onand final reports will be published in 1978.

145 149 151a. Nuclear Structure of the Odd-N Sm Isotope! m ml Sm,

1 5 3 Sm, and 15 5 Sm

;. K. Smither, D. L. Bushnell, A. I. Ninwnson, . 1). Warne r,t

K. Schreckenbach, t T. v. Fgidy, t W. F. Davidson,t 11. C. Corner, tJ. A. Pinston,t W. Stoffl, l'. Van Assche, and G. Va ndtnput

The (n, y), (n, y), and (n, e) spectra are being used to develop

the level schemes of the even-l., odd-N nuclei of 145S 149 , Sm,

153S , and Sin. The data analysis and level scheme n development has

been (_om1 letecd for 151Sm and 155Sm and papers on these nuclei are being

prepa red for publication in the Physical Review. The 151Sm and 155Sm

level schemes when combined with the previously published work on S3Sm

(Argonne and Munich), give an interesting and systematic picture of how

the low-lying levels in an even-Z, odd-N nucleus change as one approaches

the closed neutron shell at N = 82. The energy systematics of the rotational

band heads in these isotopes are shown in Fig. 39. The 155Sm level scheme

NRL/I. L. L. , Grenoble, France.

tlnstitut Langevin-Laue, Grenoble, France.

Garching/University of Munich, Munich, Germany.

S. C. K. /C. E. N. , MOL, Belgium.

125

VI. Ca,b

155

000 E(kev) 153Sm 62Sm93L 3 62 91

500 E (~E\ 6Sm-- -

U o - 3 42+ [65 1 -- _ _

r1/2 -[5211 -

a. -- (

p 3/2 -[52' 1 --- - -

5/2--[523 ' -W 3/2--[532)-' ~

I --[530) -

3/2+[402 --- -

w 500 ~ - .- 6 ]--1 12+40 ---

1000-- -

Fig. 39. E-ner'gy systematics

of the rotational bands in

15 1 Sm, 19 3Sm1, acnl 155 rm.

noticeably distorted by mixing

nearby bands. This mixing is

can be described as eight overlapping

rotational bands with a stable deformation

and very little mixing. The level ene r -

gies in each band follow quite closely

the A - I(I + 1) dependence e of a simple

rotor and the value of the constant A

does not change apprecia bly from band

to band. This stable picture changes

and becomes disto rted as one moves to

1Sm and then to S51m. The same

eight rotational bands are identifiable in

153 151both Sm and Sm, but now they are

with levels with similar spins ; 1d pa rity in

particularly 1a rge for some of the positive-

parity bands and suggests strong Coriolis mixing. The effective moment

of inertia for 1boch positive and negative bands de- reases with dec reasing

neutron number as one approaches the clos d neutron shell, N : 82, at

a bout the san e rate as it does in the adjaent even-Z, even-N Sm nclAei.

The analysis of the 15Sm and 119Sm data is still in progress but enough

has been done to suggest a marked change in nuclear structure as one goes

151 149 151 153from 51Sm to Sm. Ihe papers on Sm and 5m should be com-

pleted in 1978 and further analysis of other odd-N Sm nuclei should be

completed in 1978-1979.

b. Nuclear r Structure of 148Sm, 150Sm, 152Sm, and 154Sm

R. K. Smither, D. L. Bushnell, and G. D. Loper

The level structure of 148Sm, 150Sm, and 152Sm is being

developed through the use of (n, y), (n, e), and (n, y) (where n represents

average-resonance neutron capture) experiments. The objective of this

Wichita State University, Wichita, Kansas.

126

VI. Cb 127

Fig. 40. Average reson-ance neutron capture

data for the -1t9Sm(n, y) Sm(n s) X0m

15 0 Sm reaction. The

crosses, open c ircles, 31000 3 .4 " .and open squ;:res iden- *

tify transitions that 2' * .

2, " Eare known fr(n pr(- : .vi(.ts work t(, b I-:1,

Ml, and 1:2 transitions, z

respect:vely, for s- * M

w\ ve neutr(.n capture. - 00

Th, relative y-rayint-nsities a re dividedby '.Y5 to remove the

strong deplndence on . (E),(y ,n(r J th;t w il dLOWER LIM~T

-- \nergy that would oSENSiTvTmak1w th. idntifi cation 10

5 8of th( sub- rOup)s more GAMMA E N MeV

difficult.

work is to identify and measure the intensity of ait pus sible E1, MI1, and

E2 transitions between the lo. -lying states in thest nuclei.

T h( ; v( rag(e resonance neutron capture data ar e very useful

in this regard because they involve ave raging the neutron capture process

over many resonances. This averaging procedure nearly eliminates the

Porter-Thomr; flu rctuations normally present with neutron capture in

sinc '_c resonances and considerably reduces the likelihood of missing

any of the low-lying states that can be reached through EI or MI tran-

siticns. This averaging process is also quite useful in determining the

parity and restricting the possible spin assignment of the states fed by

these primary transitions. In the case shown in Fig. 40 for the

1.49 - 150Sm(n,y) Sm reaction the El transitions can be easily separated from

the Ml transitions purely on the basis of their relative y intensities.

The El transitions can be further subdivided into two groups: oie where

the final state is either J = 3+ or 4+ and a second where J = 2+ or 5+.

This emphasis on completeness both in finding all the low-lying levels

and all the interconnecting y rays has made it possible to identify for most

VI. Cb, c

of the low-lying states a chI racteristic y-decay pattern that can be followed

from nucleus to nucleus. The analysis of the (n, y) data is completed but

the d development of the level scheme es ha s been held up ;waiting the com -

plction of the analysiss of the Coulornib-excitation work dune on these nuclei

at the Argonne Tandem. 'A he cornbin;ttion of (n, Y) data and Coulomb-

excitation iata has been particularly useful in developing thi I evel scheme

148of rSm wher- the final lev' 1 s( heni is c onsider'ablv more complicated

than first thought. The strong 615. 01 -keV line in the (n, y) work was

unplaced in the level scheme until. it vas identified in the C oulhmb excitation

work as the gamma de(c y of a 0 level at 1 65. 4 kV V, while the comn plcex

gamma structure at 1450-1.470 keV in the Coulornb-excita tion d(hti wa s

impossible to ;analyze until the levels and corresponLnJ y r;t\'s were

ientified in t he (n, 1,) work. Sufficient infornAtic n is now a vailbl e tc

14 ,complete the level sche m , and a paper on Sm should be c m pleted in

1978 for submission to IPhvs. Rev.

C'. Neutron Capture in High Spin Isomric States in 'I N Lei

P. K. Smither, B. IHam rn e m (sh , aid I). L. Bushnell

The (n,-y) spectra fromri neutron capture in the 11/2 mta -

123 125 127stable states in Te , le, aid Te ha v. 6een used to identify high -

spin states (J -4-7) in 12T 126 , nd 128Te. The initial population

of the 11/2 isomeric state was produced by nc utron capture in the OA

Ridge high-flux reactor. 'I'h (n, y) reaction in the isomieri( state leading

to levels in the adjacent even-Z , ven-N Te nuclei was observed in the

Argonne (n,y) facility at the Argonne research renc tor CP-5 with a C( Li)

y-ray spectrometer. Identification of y rays resulting from neutron

capture in the 11/2 isormeric states was made by comnpa ring the primary

(n, y) spectra taken at Argonne shortly after the Oak Ridge irradiation

with spectra taken a year later and with (n, y) spectra using unirradiated

Cleveland State University, Cleveland, Ohio.

128

VI. Cc 129

samples. In e.ch case lines were seen that could be identified with neutron

capture in the isomeric state. The data analysis was completed last year

and a paper is in preparation for Phys. Rev.

131

VII. THEORETICAL PHYSICS

INTRODUCTION

The nuclear theory program attempts to deal in a compre-

hensive way with most of the central problems of theoretical nuclear r

physics. We emphasize (a) the systematic study of nuclear structure and

the exploitation of the best possible nuclear-structure information to

understand diverse nuclear phenomena, and (b) the development of advanced

computing techniques for theoretical physics and the application of those

techniques to the major computational challenges that arise in nuclear

theory. We also carry on a smaller program of resea rch in atomi -

molecular theory and in elementary pa rticle theory.

Current trends and highlights include the following.

A. Heavy-ion reaction theory. Last year's DWBA calcula -

tions of the reactions of 160 upon 2 0 8 Pb, using the Argonne PTOLEMY

program, have been continued and extended. We have now also analyzed

the elastic scattering of i60 by 2 8 Si and by 40Ca over a wide range of

bombarding energies. The main conclusion is the same as in the case

of 2 0 8 Pb. Excellent fits to all existing data can be obtained, but only with

energy-dependent optical potentials. This shows that single-channel

DWBA does not contain the necessary physics.

A major effort this year has gone into technical improvements

to PTOLEMY, in preparation for the planned extension to coupled-channel

calculations in 1978 and 1979.

A rather speculative alternative approach to the solution of

coupled-channel problems by use of a surface delta-function coupling

interaction is being investigated. If the new approach works, it willaccelerate coupled-channel calculations by an order of magnitude.

B. Nuclear-structure research. A shell-model analysisof the non-normal parity states in the ip shell has been completed to givea good representation of the observed non-normal parity states from A = 7to A = 13. Also in the ip shell, it has been shown that recent inelasticelectron scattering data on 1 4 C provide the information needed to determinethe odd-state part of the residual nucleon-nucleon interaction; calculationsare in progress. Other nuclear structure research includes an interpreta-tion of the E2 transition rates in N = 35 and N = 37 nuclides, a study ofalpha-transfer reactions for 14C and 14N targets, and an improved calculation

VII

132

of the isobaric-mass-multiplet energies in the ip shell by use of a charge-

symmetry-violating residua.l. nuclear interaction.

R. D. Lawson has completed a book, "The Theory of the

Nucien r Shell Model,'" to be published in 197S.

C. Nuclear-matter theory. Our program fO< uses on the

problems of finding valid approximations to the exact solutions C)f the

nuclear -ma tter equations znd of using the va iatc d approximate solutions

to test assumed nuclear forces. During thr past two years, calculations

based on the three-body correlations within tL Bethe-IBrueckner-Goldstone

approximation, using the full Reid potential, have been brought into

reason ble agreement with the data and the discrepancy between the BI3G

results and variational cal culatio._ i based on the hypernett' d chain app roxi-

Imation have been greatly reduced. The program for calculating the

three-body term in the BBG approximation is now being modified to include

long-range correlations induced by successive thr ce -,dy correlations in

chains of triplets. We are also improving thn three-body comput,-r pro-

grams to facilitate their application to a va riety of a ssumed nuclear fo rces.

D. Intern ediate-energy physics. Our goal is the interpre-

tation of intermnediate-energy experiments by applic'atl(o)n of a relativistic

particle theory with a phenomenologically -dete rmin d Hamiltonian, a d by

making use of the best avail ble nuclear-structure information. The ,ion-

nucleon mass ope a tor is based on the A r ronijnce model with separable

potentials in other channels. The pt rtmet( rs in the NN and NA intera tIons

are being determined, in part by anaiys is of the rea actionn n+ + d --pp. The

pion-nucleus optical potential is being recalculated to include soni effects

of pion absorption. Pion charge exchange a nd (p, Tr+) reach ions a re being

calculated to include the nucleon-correlation effects dcbduc-d from sh.ll-

model wave functions.

E. High-energy heavy -ion collisions and dlen e nucl c matter.

Relativistic Thomas-Fermi and Hartree calculations, including some rnmesonic

effects, have been completed for nuc lear rnatter with a surface. When the

parameters were chosen to agree with the property ,s of normal nuclear

matter, no abnormal solutions were found. A detailed analysis of the

applicability of the classical equations -of-motion approximation, and of

various hydrodynamic approximations, to relativistic collisions between

heavy ions has been completed. Relativistic equation-of-motion calcula-

tions for the collisions of nuclei with A = 20 and A = 40, to l laboratory ener-

gies of 500 MeV/nucleon, are being carried out.

F. Atomic and molecular physics. We have continued to

develop and improve methods for treating the multidimensional Franck-

Condon factors which arise in chemical reactions and in dissociations of

VII

VII 133

polyatomic molecules. We have also calculated collisional excitation of atomsby electrons in the close coupling approximation and in the quasiclassical

trajectory approximation, and we have used these calculations to suggest

experiments which will fully determine the final states of the excited atoms.

G. Other theoretical physics includes studies of nuclear

mass equations, weak interactions in nuclei, and quark-model calculations.

VII. A

A. HEAVY-ION REACTION THEORY

Experimental studies of nonrelativistic heavy-ion collisions

continue to focus attention on the competition between two classes of direct

reaction-peripheral and strongly-damped. Because of limitations on the

type of ion that can be accelerated with present-generation accelerators,we have a clear picture only for systems wherein at least one of the heavy

ions has a rmass number less than 40. For such systems, the total reaction

cross section or close to the Coulomb barrier is dominated by peripheral

reactions-elastic and inelastic scattering and few-nucleon transfer to very

low-lying states. As the bombarding energy increases, the peripheral-

reaction cross section quickly stabilizes and remains constant with increas-

ing energy while the fusion reaction (compound-nucleus fo rmation) rapidly

increases in probability and soon dominates or. At a sufficiently high

energy (EK m. /F:B~ 1.5 to 2), while the peripheril cross section stays

roughly constant, (rf suddenly stops increasing or even starts to dec rease

as more and more of the 'ross section goes into partial waves whosecentrifugal content is too great to support a compound nucleu% . This energy

region witnesses the onset. of strongly -damped processes-dir(ct rca (;tions

that leave the reaction products in highly -excited states. The picture for

the collision of two very-heavy ions is not clear; it is likely however that

fusion is of negligible probability and the competition between the two

different sorts of direct reaction starts immediately above the Coulorr b

barrier.

The main challenge for theories of hea vv-ion reactions,then, is to describe the relation between peripheral and st rongly-damoedprocesses. Are they basically distinct, with the strongly-damped processes

to be described in statistical terms or by microscopic dissipative models

involving friction or viscosity? Or are the two classes of direct reactionsmei v .ar es given to the extremes of what is in fact a coitinuum ofdirect ractions with no clear line of demarcation? The latt- r view is the

one that underlies theoretical efforts- such as that in the Argonne PhysicsDivision-that seek to describe heavy -ion reactions in terms of mic roscopic

quantum-mechanical (or semiclassical) direct-reaction models. The hope isthat, at least for bombarding energies up to some limit far enough abovethe Coulomb barrier to be of interest, peripheral and strongly-dampedcollisions can be described in terms of a multichannel reaction theory wherethe channels refer to energy-averaged giant resonances rather than toindividual nuclear states. It remains to be seen, of course, whether thenumber of such 'channels' is small enough to be tractable anod whether theknown giant resonances suffice to provide the observed transfer of mass,charge, and energy.

1 34

VII. A

In the past year, we believe that we have made significant

progress in three ways towards our goal of a multichannel treatment of

heavy-ion reactions.

16 208(1) In studies of peripheral reactions of 0 on 2N

(see Sec. VII. Ab below), we find that DWBA cross sections, after following

the energy dependence of observed transfer cross sections through the

Coulomb barrier, suddenly break and increase much too steeply. ihebreak-point seems to occur in roughly the energy region where strongly-

damped processes start to supplant fusion as the dominant part of the total

reaction cross section. We may in fact be seeing the influence e on specificperipheral channels of competition with strongly-damped processes. If

this can be established, it will provide a vital test of desc riptions ofstrongly-damped processes; we can study the evolution in energy of such

processes starting from near-barrier phenomena which we be i !hat whave underr reasonable control.

(2) Any multichannel description of heavy -ion rea ctions must

overcome severe computational problems associated with the s rong Coulomb

fields and large angular-momentum ranges endemic to heavy-ion collisions.Such problems must be thoroughly tamed in the single-chanrnel frameworkbefore reliable multichannel extensions can be contemplated. W(' believe

that the speed and accuracy of our computer program (Ptohlmy) in car trying

out single-channel calculations of various descriptions (elastic, inelastic,and transfer, as described in Sec. VII. Aa below) indicate that the ancillary

numerical problems are under adequate control. We are ready to tackle

many -channel calculations with some hope of significant success.

(3) Tcsting coupled-channel programs either use the

highly -questionable zero-range approximation or are too slow to pe rnit

the inclusion of more than one or two physical channels. None of them

are capable of handling systems such as 1 2 C or 160 on 208 Pb at energiesmore than about 1. 5 times the barrier height. Now a significant factor in

the great speed of our single-channel DWBA program Ptolemy is the use it

makes of the smooth behavior with changing angular momentum of the heavy -

ion scattering amplitudes and wave functions. We believe that this smooth-

ness can be exploited in the solution of the coupled equaLions of multichannel

problems with a gain in speed comparable to that achieved in single-channelDWBA. The necessary equations and the associated ite native procedure

have been formulated and are now being implemented. (See Sec. VII. Ad.)

We can summarize our long-term objectives as we did in ourreport of one year ago. We are heading 'towards a fully quantum-mechanicalmultichannel approach to heavy-ion direct reactions with the channelscorresponding, not to individual nuclear states, but to energy-averagednuclear excitations or giant resonances. "'

1 35

VII. Aa

a. Ptolemy: A Computer Program for Heavy-Ion Direct Reactions

M. H. Macfarlane and S. C. Pieper

In the past few years we have been developing a program

(Ptolemy) for the analysis of heavy-ion-induced direct reactions. Heavy-

ion inelastic -scattering calculations are made difficult by the large radii

and angular momenta that enter the Coulomb-excitation component of the

reactions. Previously-available DWBA programs for heavy-ion inelastic

scattering were slightly-modified light-ion programs that were too slow or

were limited to quadrupole (2 ) excitations. Ptolemy now includes an

inelastic -DWBA section, with deformed-optical-model form factors wnich

can handle all natural-parity excitations (1 , 2 , 3 , 4 , 5~, -)and

in which Coulomb contributions are treated efficiently. This part of

Ptolemy has been used extensively in collaboration with Rehm, Erskine,

Henning, and Kovar to analyze 160-induced inelastic -scattering experiments

carried out at the ANL Tandem Van de Graaff. With the addition of the

capacity to perform inelastic calculations, Ptolemy can now be used to make

optical-model fits to elastic data and DWBA calculations both for inelastic

excitation and few-nucleon transfer.

Ptolemy was originally designed to use optical potentials of

the Woods-Saxon form in the elastic channels. During the past few years

the need for more sophisticated potentials (such as folded potentials) has

been recognized. We have changed Ptolemy to allow the user to supply a

separate subroutine of a special sort, referred to as a linkule, to compute

the potential. The linkule is so constructed that the user does not need to

recompile Ptolemy, nor make a private version of it, in order to specify

a potential of arbitrary shape.

The elastic and inelastic scattering of t2C from 12C and of

160 from i60 has recently been found to have an interesting dependence

on the bombarding energy. To permit the analysis of this and similar data,

we have modified Ptolemy to treat elastic, inelastic, and transfer reactions

between identical nuclei (both bosons and fermions).

136

VII. Aa, b

The optical-model fitting section in earlier versions of

Ptolemy could accommodate data at more than one bombarding energy,

but only for one projectile and target. We have extended this part of the

program to allow data for several different elastic reactions to be fitted

with one set of optical parameters.

The above improvements of Ptolemy are extensive enough

to require a new version of the Ptolemy manual. 'this manual, which

exceeds 100 pages, has now been produced (ANL-76-11, Rev. 1).

b. Energy Dependence of Single-Nucleon Transfer Reactions Induced

16o Ions on 2 0 8 Pb

M. H. Macfarlane, S. C. Pieper, D. G. Kovar, aclnd C. Olmer

The studies of 16O-induced elastic scattering and transfer on

Pb described last year have been continued and extended. In the past

year, elastic scattering and the reactions 208Pb(16 15N) 209Bi and

208Pb(16 15 209Pb have been studied at 312.6 MeV on the LBL 88-in.

cyclotron. With the earlier Berkeley experiments at 104, 138. 5, and

216.6 MeV and a previously-published Minnesota experiment at 68 MeV, we

now have measurements of transfer cross sections extending from below the

Coulomb barrier to a laboratory energy of 312.6 MeV (P /. 4).c. m. B

No other heavy-ion peripheral reaction has been studied over a comparably-

wide range of energies. There were indications from the lower - energy

data that the energy dependence of DWBA transfer cross sections is serious -

ly at variance with experiment. These conclusions are confirm ed and

greatly strengthened by analysis of the 312.6-MeV data. Our main con-

clusions from data over the full energy range are as follows.

(1) The relative cross sections of transitions to different

single-particle and single-hole states are well reproduced by the DWBA

calculations at each of the energies under consideration.

(2) The DWBA transfer cross sections increase more rapidly

than experiment between 104 and 312.6 MeV. The discrepancy amounts to

1 37

VII. Ab, c

a factor of six for the reaction (16 15N) and is somewhat smaller for16 150) and (16 17

The fact that the ratio of DWBA to experimental cross section

is almost state-independent (the relative spectra at each energy are well

reproduced) suggests that the discrepancy in the energy dependence is a

many-channel phenomenon. If it were a few-channel effect, requiring

explicit inclusion of coupling to only a few states of each of the nuclei

involved, the ratio a-DWBA exp would probably be strongly state-dependent.

What is inescapable, however, is that a serious breakdown of the conven-

tional DWBA description of peripheral reactions has occurred. It is

tempting to relate the energy at which the energy dependence of the DWBA

cross sections breaks away from experiment to the energy at which the

fusion cross section for 60 on 208Pb starts to decrease and strongly-

damped processes start to dominate the total reaction crcss section.

Unfortunately ambiguities in the elastic data prevent us from identifying

clearly the break-point in the energy dependence and fusion data are

lacking in the critical energy region. Two papers on the question of

energy dependence have been submitted to Physical Review C.

c. Elastic Scattering of Heavy Ions

M. II. Macfarlane and S. C. Pieper

In previous years we carried out an extensive analysis of

16 208the elastic scattering of 0 from Pb. Our conclusion was that the

available data require optical potentials with a dependence on the bom-

barding energy. Given a dependence of the optical parameters on the

bombarding energy, many excellent fits to all of the data could be found.

We have now analyzed the elastic scattering of i60 on 28Si and 0 on 0a

in a similar fashion. In both cases the data cover a large range of bom-

barding energies, The conclusions of this study are the same as for the

study of 0 + 208Pb: the elastic data require energy-dependent optical

1 38

VII. Ac-e

potentials if good fits are to be achieved at all energies. This research

was reported at the Rochester Symposium on Heavy-Ion Elastic Scattering.

d. Light -Ion -Induced Direct Reactions

M. H. Macfarlane and S. C. Pieper

In two areas of research with light -ion-induced direct

reactions work is being significantly impai-:ed by lack of fast, accurate

finite-range DWBA programs. These areas are (1) single-nucleon

transfer reactions [(d,p), (pd), (t,d) . . . ] with polarized beams and

(2) transfer reactions [ (d,p), (pd), - - - ] at intermediate energies

(laboratory kinetic energies from 50 to 500 MeV). Test runs indicate

that with a modicum of tuning, Ptolemy can carry out finite-range light-ion

transfer calculations at speeds comparable to those of the best zero-range

programs. Practical applications will require that Ptolemy be extended

to include projectile spin-orbit effects in both the fits to the elastic

scattering and in the transfer calculations, to provide for the input of a

variety of forms for the deuteron and triton wave functions (including

D states), and to compute polarizations and analyzing powers. The

necessary formal expressions are at hand; it remains to program them

for inclusion in Ptolemy (about one to three man-months of work).

e. Coupled Channels for Inelastic Excitation

M. H. Macfarlane, S. C. Pieper, and M. Rhoades -Brown

The conclusion of Sec. VII. Ab above was that the single

channel DWBA cannot adequately account for the energy dependence of at

least some heavy-ion transfer reactions. K. E. Rehm et al. (see

Sec. III. 3a of the Heavy-Ion Physics section of this report) have demon-

strated that coupled-channel calculations are required to account for certain

features of their data for the inelastic scattering of 160 from isotopes of

Ca. We have been developing the formalism necessary to include coupled

139

VII. Ae, f

inelastic channels in Ptolemy. Our approach will be somewhat different

from that used in other coupled-channels programs.

The equations for the largest value of the total angular

momentum will first be solved as uncoupled equations. Since the nuclear

force is weak in the largest partial waves, this first solution should be a

good estimate of the exact solution. This first solution will then be substi-

tuted in the coupling terms to convert the coupled equations in a set of

uncoupled inhomogeneous equations from which a better estimate of the

solution to the coupled equations can be generated. This iterative process

will be continued until convergence is achieved. The solutions for lower

values of the total angular momentum will be found by the same iterative

technique; however, the initial estimate of the inhomogeneous term will be

based on the solutions for higher angular momenta. The well-known

(but little exploited) smoothness of heavy-ion reaction amplitudes with

respect to angular momentum should make this a rapidly-convergent process.

f. Surface Delta Potential for Coupled-Channel Problems

R. D. Lawson

An alternative approach to the solution of coupled-channel

problems, applicable to light-ion scattering and Tr-meson scattering as

well as heavy-ion scattering is to replace the coupling terms by 6 functions.

One has to solve coupled differential equations governed by th( Hamiltonian

H = p2/2m + V(r) + YfLa.(r) [ YL 0 T ', 00'La

where TL(O, () is a nuclear tensor operator of rank L (for example, the

quadrupole operator when L = 2), a denotes the various nuclear levels,

YL(0,<) is the spherlLal harmonic of the projectile and [. X . . ]00denotes the coupling of the two operators to angular momentum zero.

Usually fLa(r) is assumed to have nonzero values only near the nuclear

surface. If one goes to the extreme that

140

VII. Af

fLa(r) = VLa6(r - RLa

where VLa is a constant, then the differential equations become uncoupled

except at the point r = RLa. Thus for r RLa, one has a system of un-

coupled equation that can be simply solved numerically. The solution for

all r involves equating the value and discontinuity in slope for the various

channels at the point r =R La. With this approximation one has, therefore,

converted the problem from one of solving coupled differential equations to

one of solving uncoupled equations plus the inversion of matrices whose

elements depend on VLa and the values of the various channel wave

functions at the point R.

At the moment it is not clear when or to what extent the

6 -function approximation is an adequate representation of the coupling

potentials. However, if it is, a large step forward has been made since

the solution of coupled equations is extremely time consuming. Crude

estimates indicate that with the 6-function coupling, the solution of the

coupled equations should be speeded up by at least an order of magnitude.

141

VII. Ba

B. NUCLEAR STRUCTURE STUDIES

We have continued to search for effects which lead to im-

proved understanding of nuclear structure. The system of Argonne Shell-

Model codes is continuously upgraded to improve our ability to calculate

such effects. A primary objective is to determine the effective nucleon

interaction that is fundamental for nuclear theory. That part of our study

which concerns non-normal parity states is made possible by the ability

to remove spurious center-of-mass excitation in the Argonne codes. This

is important in studying El gamma decays which are generally observed to

be severely inhibited and often provide severe tests for a nuclear model.

We plan to continue our research on non-normal parity states

in the ip shell and lower sd shell where the structure of normal parity

states is well known. The results can then be used to test gamma tran-

sitions and multiparticle transfers between the two types of states. They

are also pertinent to tests of parity mixing in nuclear levels.

For heavier nuclei in the A = 40 to 56 region a specialized

program has been written in collaboration with Mller-Arnke in order to

expand the usual (f 7 / 2 )n space by allowing one particle to be excited to the

f5/2 orbit. This may be sufficient to improve calculations of magnetic

moments, Ml gamma decays and allowed beta decays.

a. Non-normal Parity States of the Ip Shell

D. Kurath and W. D. Teeters

We have calculated the energy spectra of nuclei between A = 7

and A = 12 for states resulting from the configuration (0s)4()A-5(s I)

and (Os)3(1p)A -3. This is a continuation of our previously reported work

for A = 11 and 13. In all cases this model gives a good representation of

the observed low-lying states of not-normal parity. The most interesting

feature is the relative importance of the (05)3 component as a function of

mass number; it is calculated to be especially strong for nuclei with

A = 4N - 1.

Strikingly similar results have recently been reported by

a group in East Germany, although the part of their interaction involving

Os nucleons differs considerably from ours. We are seeking the reason

142

VII. Bab

for this great similarity and also looking for differences in predictions of

the two calculations which can be tested experimentally.

In addition to making a more careful study of that part of

the interaction involving Os nucleons, we plan to study sonic nuclei with

A = 4N - 2 wherein the (Os)2(Ip)A-2 component may be very important.

b. Odd-State Interaction within the Ip Shell

D. Kurath

Although the even-state (spatially symmetric) part of the

residual nucleon interaction within the ip shell is quite well determined

empirically by a fit to tie spectra of low-lying states, the odd-state

(spatially antisymmetric) part of the interaction is poorly determined.

However, recent experiments have determined properties for some states

which are sensitive to the odd-state interaction. In particular, inelastic

electron scattering on 14C shows that the I state lies some 1. 5 MeV

below the excitation energy calculated with the empirical interaction and

that the B(M1) is about half the calculated value.

An interesting correlation exists between this transition and

the MI transition between the two lowest 1/2 states of 13C. If the calculated

wave functions of these states are written in the form of a lp-neutron14

hole coupled to states of C, the dominant component of the 1/2 ground

13 14state of C is a p)/2 hole coupled to the C ground state, and the excited

+ 141/2 state is a p 1 / 2 hole coupled to the I state of C. This explains why13

the calculated strength of M1 transitions from the C ground state to all

other 1/2 states lies almost entirely in the single transition above. It

also means that the B(M1) between the 1/2 states of the 13C should be the

same as the B(M1) measured in (e, e') on 14C, which is in agreement with

experimental observation.

We plan to incorporate the new data in order to make a

better determination of the odd-state part of the residual interaction.

1 43

VII. Bc

c. Interpretation of Large E2 Differences in Isotopes with N = 35 and 37

D. Kurath and R. D. Lawson

Isomeric lifetimes have recently been measured at Argonne

in isotopes of 28Ni, 30Zn, and 3 2 Ge having neutron numbers N = 35 and 37.

For common low-lying 5/2 and 1/2 states the ratio of BE2(5/2 -> 1/2 )

val'i;2s

R - [ BE 2 (N = 35)/BE 2 (N = 37)]

was found to be R = 55, 15, and 13, respectively, for Ni, Zn, and Ge

isotopes. Above N = 32, neutrons are filling the 2 p 1 / 2 and If 5 / 2 levels;

and the behavior of R can be interpreted as due to the degree of occupation

of the If5/2 level.

This can be seen in the most simple model, assuming wave

functions

1/2~(n) = p X [fn-1]I=0

where n - N - 32, p 2 p1 /2 , and f = if5/2

45/2 2 [fn] 5/2 + 2 -2] 5/2

1 - a2n

Any neutron interaction containing the usual strong-pairing feature would

2lead to fairly small an values with a 3 negative and a 5 positive. Hence

R = {2 - a 3 - [8a(1 - a)] 1 }/{1 + a2 - [8a2(1 - 2 1/23 5 5)

and large R values are due to near cancellation in the denominator. For

2 2example, the Zn value, R = 15, can be obtained with a3 =0. 1i and a5

J

= 0. 20. An added check on these values lies in the ratio of quadrupole2 2,

moments of the 5/2 states since [ (Q) n=3 /(EQ) = - ' 3 /(1 - a 5 ).

The measured EQ moments for the Zn isotopes lead to a ratio of -0. 15,

which is consistent with the value resulting from the a's determined by R.

An alternative model would consist of coupling p and f

neutrons to 0 and 2 vibrational states. Here the change in sign of Q_,

144

VII. Bc, d

the neutrons' quadrupole moment, in going from N = 35 to N = 37, would

affect the coupling with protons (Q X Q ). This will determine the BE2

ratio, but the underlying reason is the same, namely, the degree of filling

of the If5/2 neutron level.

d. Alpha Transfer for 14C and 14N Targets

D. KurF.th and H. T. Fortune'

The alpha-transfer reaction ( Lit) with A=14 targets can

be related to other cluster-like transfer reactions since the A=14 nuclei

are well represented as two ip holes in 160. The type of related transfer

depends on the nature of the states of the final nucleus.

The 14C(7Li,t) 80 reaction to positive-parity final states

proceeds both by transferring all four nucleons into the sd shell and by

transferring two protons to the ip shell and two neutrons into the sd shell.

The latter amplitude is related to the 16O(tp)180 reaction wherein the

squared amplitude to different final states is determined. However, the

alpha transfer depends on the relative phases of the two contributing

amplitudes and tests the theoretical picture of this process. Satisfactory

agreement with experiment has been obtained in a paper accepted for publi-

cation. A similar treatment is planned for the 14N( Li,t) 18F reaction,

wherein deuteron transfer to i60 is relevant.

Some negative-parity states of 180 have the nature of a

19p 1 / 2 proton hole coupled to states of F. The probability of exciting such

14 7states in the C( Li,t) reaction is related to the triton transfer reactions

such as (a,p) on 15N and 0 targets. Thus all three reactions should be

related if cluster transfer is dominant.

University of Pennsylvania, Philadelphia, Pennsylvania.

1 45

VII. Be

e. Evidence for an Isotensor Nucleon-Nucleon Interaction

R. D. Lawson

Provided isospin is a good quantum number, the energies

of states with given I and various values of T are related by the isobaricz

mass -multiplet equation

E=a+bT +cT (1)z z

The experimental values of c have been determined for the ip-shell nuclei

and compared with theoretical estimates. In order to estimate c, the

two-body Coulomb interaction was calculated using a Woods-Saxon potential

plus the effect on the proton of a uniform charge distribution. The binding

energy of the proton was taken to be

BE ( XN(I, T) - BE(4He 2 )

(A - 4) ' (2)

where BE (XN(1, T) is the negative of the binding energy of the nucleus

A

ZXN in the state (I, T)-in other words, each of the valence p-shell nucleons

was assumed to have the same binding energy. We have also calculated the

Coulomb energy in other ways and this method seems to give a slightly

larger theoretical valu for c than other reasonable prescriptions.

However, even when c is calculated in this way, one always underestimates

its value. When the electromagnetic (v/c)2 corrections, vacuum polariza-

tion, the effect of finite neutron and proton size and short-range correlations

are included, the results given in column 5 of Table III are obtained. In all

cases except one the predicted value of c is too small. In addition the three

worst cases, the I=3/2 T=3/2 state in A = 9 and the two 0 states, corres-

pond to seniority one and zero. Their rms error is 51 keV compared to

20.7 keV for the eight higher seniority levels. This is precisely the

situation that would occur if a short-range isotensor interaction had been

omitted.

146

VII. Be

TABLE III. Values of c, Eq. (1), for the ip-shell nuclei. Column 5gives the theoretical value when the Coulomb interaction including (v/c) 2

corrections, vacuum polarization, the effect of short range correlations

and the finite size of the neutron and proton are all included. The last twocolumns give the predicted value when the short range isotensor interaction

of Eq. (3) is included.

A I T c in keV

Expt. Best V = 0. 175 MeV V = 0. 202 MeV

electromagnetic Q = 1 Q = 0. 241

1 1 208 202 218 213

8 2 1 223 200 210 207

3 1 -223 220 245 242

1 3 240 210 231 2289 2 2

j 3 264 216 237 2342 2

10 0 1 363 300 352 358

2 1 297 264 301 304

12 1 1 246 225 245 243

2 1 208 219 234 224

13 3 3 256 239 265 261

14 0 1 338 299 349 351

rms error in keV 31.9 15.3 14.2

The last two columns give the computed value of c when the

interaction

- e r 1 2

V = V {P + QP }{rz(7) z(2) - -i(1) - r(2)} (3)

is included. [When V = 0. 3 MeV, the (np) interaction is 2% more attractive

than the (nn) or (pp).] A best fit to the p-shell data gives V = 0. 175 MeV

147

VII. Be, f

when a spin-independent potential is considered (Q = 1) and V = 0.202 MeV

when a spin dependence is allowed. Clearly there is a marked improvement

in the fit to c. Not only is the seniority dependence of the rms error

eliminated but also one now overestimates c about as often as one under-

estimates it. Details regarding the strength and spin dependence of this

added potential would require that we be able to calculate the electromagnetic

effects at the 5-keV level and this we have not done. However, the need

for such a potential seems clear from the fact that without it we consistently

underestimate c and moreover have a marked seniority dependence of the

rms error.

f. Isospin Mixing Between T=0 and I States in the ip Shell

R. D. Lawson

Off-diagonal matrix elements between T=0 and 1 states in

the ip shell are calculated using different proton and neutron wave functions

to evaluate matrix elements of a charge-symmetric nucleon-nucleon1 2

interaction. To do this we assume the Cohen-Kurath and Kumar inter-12 8

actions are appropriate for the (np) interaction in C and Be, respectively.

We then assume the T=1 potential that gave rise to these matrix elements

has a Gaussian form and a Rosenfeld spin dependence

v~p 5 2 2V = VO 9 P1} exp - r 1 2 '

where PO and P1 are the spin-singlet and triplet projection operators and-1 12

= 0.575 fm . In C the average binding energy of a proton relative to

He is 4.69 MeV and for a neutron is 7.46 MeV. Matrix elements of the

Gaussian potential are evaluated using proton and neutron wave functions

corresponding to these binding energies and the T=1 (np) interaction is

taken to be the average of the (nn) and (pp). With these assumptions, the

S. Cohen and D. Kurath, Nucl. Phys. 73, 1 (1965).

2 N. Kumar, Nucl. Phys. A225, 221 (1974).

1 48

VII. Bf, g

TABLE IV. Values of the off-

diagonal matrix element in keV. a is the

diffuseness parameter of the Woods-Saxon

potential, V = V1{ + exp(r - R)/a} andR = 1.2 A1/3 fm.

a in fm 0.65 0.50 0.02

2 in 8 Be 225 187 117

I in 12C 209 170 103

appropriate (nn) interaction to be used in 12C is simply

[((nn) V (nn))/' {((nn)I V (nn)) + ((pp) V I(pp))}]

times the Cohen-Kurath value and an analogous change for the (pp) matrix

elements.

In Table IV we list the contribution to the off-diagonal matrix

element brought about by this wave function size effect as a function of a,

the diffuseness parameter of the Woods-Saxon potential. (The appropriate

binding energy in 8Be is 1.94 MeV for a proton and 3.71 MeV for a neutron.)

This is a large effect and extremely sensitive to the shape of the wave -

functions used to evaluate it. Until this can be accurately taken into account,

it will be impossible to extract information about a charge-symmetry-

breaking interaction from a measurement of these off-diagonal matrix

elements.

g. Properties of the f7/2 Nuclei

A. Muller-Arnke* and R. D. Lawson

A program has been written which allows one to do shell-

model calculations in which one particle is excited out of the If7/2 shell to

the f 5 /2, p 3 /2, or p 1 / 2 orbits. This program has been used to calculate

Technische Hochschule, Darmstadt, Germany.

1 49

VII. Bg,h

E4 and E6 properties of the f7/2 nuclei, and it has been found that one-

particle excitation is not sufficient to account for the observed properties

unless a substantial polarization charge is assumed. The interesting thing

about this result is that the polarization charge must be positive at the

beginning of the shell and negative at the end. We intend to examine the

effects of one-particle excitation on the magnetic properties of these nuclei,

particularly the magnetic moments, the MI gamma decays and the beta

decays. This project will be mainly carried out using the excellent com-

puting facilities of the GSI in Darmstadt.

h. Theory of the Nuclear Shell Model

R. D. Lawson

A book dealing with phenomenological nuclear -shell-model

calculations has been completed. This book is designed to fit the needs of

experimentalists and theorists who wish to interpret data. The standard

tools of angular momentum algebra are explained and, whenever a new

concept is introduced, it is immediately applied to the interpretation of

experimental data. This book, which is estimated to be 536 pages, will

be published by Oxford University Press in the spring/summer of 1978.

A list of chapter titles follows:

(1) Single Closed Shell Nuclei

(2) Neutron-Proton Problems

(3) Particles and Holes

(4) Harmonic Oscillator Wave Functions

(5) Electromagnetic Properties

(6) Quasi-particles

(7) Poor Man's Hartree-Fock

In addition, there are seven appendices in which many

useful formulae are deduced.

150

VII. Bh 151

(A) Clebsch-Gordan Coefficients

(B) Reduced Matrix Elements

(C) Quasi-spin and Number Dependence of Matrix Elements

(D) Racah and 9-j Coefficients

(E) Fractional Parentage Coefficients

(F) Relative-Center-of-Mass Transformation Coefficients

(G) The Rotation Matrix

VII. Ca

1C. NUCLEAR MATTER THEORY

Homogeneous nuclear matter is an important testing ground

for.the adequacy of assumed nuclear forces, provided we can find valid

approximations for the equations that determine the exact coupled-cluster

amplitudes.

The main tool in reaching this goal is comparison of different

approximations with each other and with variational upper bounds for the

energy per particle. In this context we have followed three complementary

lines of investigation: (a) numerical solution of appropriately truncated

coupled-cluster equations for the full Reid potential, (b) an investigation of

model Bose gases by several different approximations, (c) a critical

investigation of the upper-bound properties of energies obtained by the Fermi

hypernetted-chain method.

From our earlier work, we have available accurate calcula-

tions of the two-body and three-body terms in the Brueckner-Bethe-

Goldstone (BBG) approximation for the full Reid potential. At densities

near and slightly above the empirical saturation density, the resulting

energy is in reasonable agreement with variational calculations. However,an adequate calculation has not yet been done with either method, and large

discrepancies between them remain at higher densities.

B. D. Day, Rev. Mod. Phys. 50, 495 (1978).

a. Solution of Three-Body Equations in Nuclear Matter

B. D. Day

The implementation of any method for calculating the

properties of nuclear matter, such as the Brueckner-Bethe-Goldstone (BBG)

approximation, requires an accurate solution of the Bethe-Faddeev three-

body equations. The three-body amplitudes are needed to make tests of the

validity of the scheme and, if the scheme proves valid, to calculate the

resulting approximation to the energy.

In earlier work we have found that such calculations are

feasible in momentum space. Tensor forces, spin-orbit forces, and all

the other complexities of the nuclear force are properly treated in the

three-body calculations. An angle-average approximation to the Pauli

152

VII. Ca

operator is used, and this causes an uncertainty of several tenths of a MeV

in the three -body contribution to the energy at densities slightly above the

empirical saturation density. This approximation can be improved if that

later becomes necessary.

We have made two improvements in the three-body program.

First, the earlier version calculates the correlation energy of a particular

triplet of particles, say particles 1, 2, 3. However, successive three-body

correlations among different triplets, e. g. , 1, 2, 3, then 1, 2, 4, then

2, 4, 5, etc., can build up long-range correlations. Earlier work by

Zabolitzky on light nuclei indicates that such "ring correlations" may be

important in nuclear matter. Therefore, we have modified the three-body

calculation to take account of these correlations.

The second improvement is a technical one. The three-body

program uses large matrices, and the earlier version requires that certain

numerically-small terms be dropped in order to fit these matrices into

the fast memory of the computer. Arranging to have the omitted terms

acceptably small while the matrices do not grow too large requires many

time-consuming test runs, and this tedious process must be repeated for

each new two-body potential. Therefore, we have developed a method to

include the small terms by perturbation theory without increasing the size

of the matrices. This will greatly reduce the amount of time that must be

devoted to testing.

A computer program incorporating both improvements, valid

for the most general nuclear force, is being debugged. It will first be used

to calculate the effect of long-range correlations and to make calculations

for simple central potentials, for which accurate variational results are

available for comparison. If the results are favorable, we will then treat

the full Reid potential and other realistic models of the nuclear force.

153

VII. Cb, c

b. Model Bose Gases

F. Coester, B. D. Day, and J. G. Zabolitzky

The equations for the coupled-cluster amplitudes of a Bose

gas are simpler than those of a Fermi gas. But they are sufficiently similar

that insights into the validity of approximations for bosons can guide more

elaborate Fermi-gas calculations. We are studying model Bose gases with

3 1four different potentials: the Reid S1 and S0 potentials, the repulsive part

of the Reid S0 potential, and the hard-sphere potential. Good variational

energies are available for comparison in all these cases. A simple

approximation has been found for repulsive potentials that, although its

accuracy is only 15-20%, works equally well over a remarkably large

density range (up to at least 10 times the empirical saturation density of

nuclear matter). We are continuing this work with the purpose of sub-

stantially improving the accuracy of this approximation and extending it to a

more general class of potentials.

c. Fermi-Hypernetted-Chain Methods for the Ground State of Fermion

Matter

J. G. Zabolitzky

The convergence properties of the Fermi hypernetted-chain

method as originated by Fantoni and Rosati have been investigated.

Numerical results have been obtained for liquid He and for two model fer -

mion liquids with central potentials. It turns out that for not-too-high

densities and not -too-long -ranged correlation functions, the convergence

to an upper bound for the ground-state energy is excellent, but that for

higher densities and/or longer-ranged correlation functions, it is easily

possible to underestimate the upper bound if one does not apply certain

convergence criteria and associated error estimates. This work was

published in Phys. Rev. A, September 1977.

1 54

VII. D 5

D. INTERMEDIATE ENERGY PHYSICS

1. RELATIVISTIC PARTICLE QUANTUM MECHANICS AN

APPLICATION TO INTERMEDIATE ENERGY

HADRON-NUCLEUS REACTIONS

F. Coester and T. -S. H. Lee

The elementary degrees of freedom in a relativistic quantum

theory may be either local fields or particles. In either case, the

relativistic transformation properties are implemented by unitary operators

on the Hilbert space of states. For free fields and noninteracting particles,the theories are equivalent. For interacting systems quantum field theory

and relativistic particle quantum mechanics are radically different. In

field theory, infinitely many degrees of freedom and locality are essential

for relativistic invariance. In a particle theory the number of degrees of

freedom may be finite and the dynamics is governed by an invariant mass

operator rather than a local stress-energy tensor.

A many-particle theory can provide a useful description of

intermediate-energy hadron-nucleus reactions. The major advantage is

that we have an inherently-consistent description that accormodates both

the nonrelativistic many-body structure of finite nuclei and the relativistic

velocities of the incident hadrons. The major outstanding fundamental

problem is the correct introduction of fields (specifically electromagneticfields) into such particle theories. Its solution is needed to describe

electromagnetic effects in relativistic nuclear reactions.

Our present studies on the intermediate energy pion-nucleus

interaction are based on a many-body Hamiltonian which can account for

both the scattering and the absorption of pions by nuclei at energies near

the (3,3) resonance. The many-body Hamiltonian is determined from mass

operators for the pion-nucleon and nucleon-nucleon subsystems. The pion-

nucleon mass operator includes the rN : A mechanism in the (3,3) channel

and separable interactions in other partial waves. The same A degree offreedom is then used to determine the NN mass operator which includes

separable interactions for NN 2 NN and NN : NA transitions in each partialwave. The parameters of these mass operators are determined by fittingthe available rN and NN scattering phase shifts, and the cross sections ofthe rr+ + d - p + p reaction.

The main purpose of using the separable interactions in alltwo-particle channels is to facilitate the many-body calculations for thepion-nucleus interactions. We study various pion-nucleus reactions at

155

VII. Dla,b

energies near the (3,3) resonance and compare the consequences of our

model to recent experimental data. In this energy region, the most

important channels are the elastic, quasi -elastic, and pion -absorption

channels. Previously, we have developed a model that could account for

elastic and quasi-elastic scattering but does not include an absorption

mechanism. The main feature of our new model is the addition of pair

absorption by the mechanism 7 + N + N -+NA -+NN. We first tested this

mechanism by studying the absorption of pions by 4He with encouraging

results. We are now in the process of incorporating this absorption mechan-

ism into the optical potential and calculating various pion-nucleus reaction

cross sections.

a. Determination of the Hamiltonian Parameters

T. -S. H. Lee

We are determining the parameters in the NN and NA

interaction by fitting the cross sections for nucleon--nucleon scattering and

7+ + d --+ pp reaction. We have fitted the parameters for partial waves that

contribute to the 7+ + d -+ pp reaction, neglecting channels with more than

one pion and all interaction in the rNN channel. A paper for publication

in Physical Review is in preparation. In 1978 we plan to fit other partial

waves, test the validity of the simplifying assumptions and remove them if

necessary.

b. Fast Proton Emission from the Absorption of a Pion

T. -S. H. Lee

To test the absorption mechanism 7NN - NA -+NN, we have

+ 4studied the reaction .. + H -+p + - - - for high-energy protons. We

assume that in this process the interaction between the active pair of

nucleons and the spectators is negligible. Preliminary calculations have

shown within this dinucleon impulse approximation that our separable

model Hamiltonian can reasonably account for the data in the region

where two-nucleon emission is dominant. We expect to complete this work

in 1978. This success encourages the next step, which is to incorporate

our absorption mechanism into the pion-nucleus optical potential.

156

VII. D1 c,d 5

c. Pion-Nucleus Optical Potential

T. -S. H. Lee

An adequate pion-nucleus optical potential must involve the

effects due to coupling between the ela stic channel and both the quasi-elastic

and the pion-absorption channels. Our previous model of the first- and the

second-order optical potentials involved only the effects of the quasi-elastic

channels. The dinucleon impulse approximation described in Sec. VII. Dib

and the simplicity of the separable interactions makt explicit computation

of the absorption effects on the optical potential feasible. We are in the

process of extending our optical-model computer program to include these

absorption effects. We plan to apply this ln\w optical potential to the

forthcoming la rge-angle pion-nucleus plastic scattering data. This optical

potential will also be used to examine various pion-nucleus reactions which

will be described below.

d. Pion-Nucleus Inelastic and Single -Charge - Exchange Scattering

D. Kurath, R. D. Lawson, and T. -S. I. Lee

Inelastic scattering and single-charge -exchange reactions

of the pion-nucleus system can be studied with our general computer

program which calculates the distorted-wave Born approximation in

momentum space. The interaction leading to inela stic transitions and

the optical potential are constructed in a relativistic many-body theory as

described above.

In addition, we use the Argonne shell-model programs to

obtain the nuclear correlation needed in the reaction calculations. A large

amount of data on the above reactions is being obtained by the Argonne groups

as well as by other laboratories. In 1978 we plan to study those nuclei

whose properties are well represented by the shell model.

157

VII. Die,f

e. Pion-Nucleus Double-Charge-Exchange Reaction

T. -S. H. Lee, D. Kurath, and B. Zeidman

In a simple double-scattering model, we have shown that

nuclear structure can have strong effects on the pion-nucleus double-

charge-exchange (DCE) reaction. A paper describing this work has

been published in Physical Review Letters.

We are now investigating the extent to which the absolute

value of the DCE cross sections can be calculated by the mechanism of

successive scattering. The calculations are based on the second-order

distorted-wave Born approximation. Calculations for DCE on 160 and 180

are expected to be completed in 1978. Next, we plan to study Ip-shell

nuclei which may show variations of the DCE cross sections with nuclear

structure. Experimental confirmation of these variations would provide a

test of the model.

f. Study on (p, Tr ) Reactions

T. -S. H. Lee and M. H. Macfarlane

Our previous study of tnis reaction was based on the pionic -

stripping model: the pion is produced directly by the TrNN vertex inter-

action, which turns the incident proton into a neutron that is captured by

the target nucleus. We have found that in such a model the calculated

cross section is very sensitive both to the nuclear form factor and to the

pion wavefunctions. A report on this work will be prepared. We are now

repeating these calculations fo, p-shell nuclei with two significant improve-

ments. (1) Improved radial form factors are to be obtained by solution of

the appropriate inhomogeneous differential equations. These equations were

derived by Bergmen and by Pinkston and Satchler in 1965, but have been

solved only for two-particle systems. (2) The theoretical pion-nucleus

optical potential in Sec. VII. Dic will be used to generate more accurate

pion wavefunctions that involve the effects due to pion-absorption and to

short range NN correlation.

158

VII. DIf;2

Within the framework of the many-body Hamiltonian described

before, the (pTr ) reaction proceeds by NN -+NA-+NNTr. We plan to

examine this model of pion production on nuclei by extension of the dinucleon

impulse approximation to include effects of the interaction between the

incident proton and the nucleus. Because of the simplicity of our separable

model Hamiltonian, distorted-wave calculations for the (p, r ) reaction

based on this two-nucleon mechanism are expected to be feasible.

2. Tr-MESON SCATTERING BY 0

R. D. Lawson and J. P. Schiffer

The cross-section ratios -(rr ,n)/o-(r ,n) or(r ,p)/o-i(rp)

for the scattering of r mesons off free nucleons have the value 9 when the

energy of the incident pion is near the (3,3) resonance. Recently the- cross

sections for the excitation of the first 2 state in 180 by both r and iT

mesons with this energy have been measured and the ratio

- 18 + + + 18 + +o-[ T , 0(0 -+ 2+)] /o-[ T , 0(0 -+ 2+)] instead of being nine is close to

two. If one allows for core excitation in the 180 wave functions, one can

show that the ratio of these cross sections should be

- 18 + + + 18 + + +2 +6o[Tr , 0(0 -+2 )]/o-[r+ , 0(0 -+2 )] [3(1 + 6) + s]/[(1 + ) + 36] 2

where 6 is the E2 polarization charge which is assumed to be the same

for both neutrons and protons. If one describes the iow-lving states of 180

using the (Id 5 / 2 , 2s 1/) model space, one needs 6 0.89 to explain the

observed E2 gamma-decay transition rates. When this value is used,

the above ratio becomes about 2. 1 in good agreement with experiment.

159

160 VII. Ela

E. HIGH-ENERGY HEAVY-ION COLLISIONS AND DENSE

NUCLEAR MATTER

1. DENSE NUCLEAR MATTER

The present investigations arose from our earlier interests

in "collapsed" (superdense) nuclei. A part of our studies is in fact con-

cerned with problems of dense nuclear matter; much of the interest is

however now on high-energy heavy -ion collisions in general.

The possible properties of nuclear matter at high densities

have been studied with relativistic Hartree and Thomas-Fermi calculations

and an associated phenomenology which is also required to describe normal

nuclear conditions. Recent applications have been to neutron matter and

neutron stars.

The only apparent possible means of production of dense

nuclear matter is in the high-energy collisions of heavy ions at laboratory

energies greater than about 100 MeV/nucleon. Such conditions are expected

to produce transitory dense and hot nuclear matter and possible nuclear

shock-wave phenomena. There is then the question of what one can learn

about dense nuclear matter from such collisions and the more genera.

problem of understanding these collisions.

a. Relativistic Calculation of Nuclear Matter and the Nuclear Surface

A. R. Bodmer and J. Boguta

A paper with the above title is about to appear in Nuclear

Physics. In this work, which was completed during the past year,

relativistic Hartree and Thomas -Fermi calculations are made (for N = Z)

for infinite and semi-infinite nuclear matter, the latter being an idealiza-

tion of the nuclear surface for the limit of zero curvature (A = 00). Cubic

and quartic scalar-meson self-interactions were included, corresponding

to a phenomenological generalization of the interaction used by Lee and

Wick. The strength of these self-interactions and also the scalar- and

vector-meson coupling constants and the scalar-meson mass were considered

as parameters chosen to fit the empirical properties of nuclear matter and

VII. Ela,b;2a

of the nuclear surface. Acceptable fits imply large self-interactions, but

no abnormal nuclear matter solutions were found even when only the nuclear

matter properties (but not the surface properties) were required to be

correctly reproduced. The best fit for the nuclear surface gives a com-

pressibility constant of 150 150 MeV, in good agreement with other

determinations which also depend on the nuclear surface properties. The

Hartree and Thomas-Fermi results are in good agreement for large

surface thicknesses.

b. Neutron Stars in a Nonlinear Mean Field Theory

J. Boguta

The model discussed in Sec. VII. Ela above has been

supplemented with contributions from the p meson, which is an isovector.

This allows one to obtain the empirical symmetry energy for normal

nuclear densities, and extends the model to the unsymmetric core of

differing neutron and proton densities, i. e. , N # Z. In particular, this

extended model has been applied to neutron stars. An upper limit of about

15 times the solar mass is obtained for the mass of neutron stars.

2. CLASSICAL MICROSCOPIC CALCULATIONS OF HIGH-ENFRGYCOLLISIONS OF HEAVY IONS

a. Microscopic Descriptions of High-Energy Heavy-Ion Collisions

A. R. Bodmer

A review and critical assessment with this title has appeared

in the Proceedings of the Topical Conference on Heavy-Ion Collisions

(Fall Creek Falls State Park, Tennessee, June 13-17, 1977). The first

part gives a review (including recent unpublished developments) of the

classical equation-of-motion (EOM) calculations described below in

Sec. VII. E2b. The second part is a critical assessment of the various

161

VII. E2a,b

basic approaches to high-energy, heavy-ion (HE-HI) collisions, namely:

hydrodynamics, cascade and (equivalently) Boltzmann equation calculations,

and the EOM approach. The relation of these approaches to each other,

their respective domains of validity, and thus also a search for justified

simplifications were discussed for energies in the range of about 100-500

MeV/nucleon. Hydrodynamics depends on local or approximately local

thermodynamic equilibrium which is generally poorly justified in view of

the quite large mean free path (: 2 fm). If hydrodynamics is used, it should

at least include viscosity and heat transport, which are expected to give

large dissipative effects. Thus the Navier-Stokes rather than the Euler

equations should be used. Cascade calculations or equivalently the use of

the Boltzmann equation depend upon the nucleon-nucleon interaction being

of short range relative to the mean nucleon-nucleon separation, or roughly

equivalently upon the potential energy effects being small. This is not

the case for the energis under consideration; however, cascade calcula-

tions do not assume thermal equilibrium and can include the full Jx peri-

mental cross sections (including particle production) as well as relativistic

kinematics. The EOM approach depends upon quantum mechanical effects,

such as exclusion principle and degeneracy effects, being small or allowable

for. A rather detailed critical analysis of thy EOM approach has been

given. It is shown that also this approach is at best only marginally valid.

There is thus no obvious simplification available; each of the approaches

just mentioned has its own particular features of interest for HE-HI

collisions, and it seems important that each approach be adequately and

consistently pursued.

b. Nonrelativistic and Relativistic Classical Microscopic Calculations ofHigh-Energy Heavy-Ion Collisions

A. R. Bodmer, A. D. MacKellar, and C. N. Panos

This is a continuation of our previous calculations in which

the trajectories of all the nucleons are calculated classically assuming

162

VII. E2b, c

two-body forces between all pairs of nucleons. Nonequilibrium, transport

and transparency effects are thus fully included, no assumptions being

made about local or approximately local therrmodynamic equilibrium (as in

hydrodynamics); also, finite range and potential--ene rgy effects of the nuclear

forces are included. A detailed study is in progress of the collision of

nuclei with A = 20 and A = 40 for laboratory 'nergies from about 100 to

500 MeV/nucleon. Both nonrelativistic and relativistic c:;1culations are

being made, the latter to order of .v2/2. The r lativistic cAculations

in addition to including relativistic "kin natic" r ad kinetic --cn'frgy effects

also include relativistic (reta rded) corr actions t tht 1luclea forces.

Such corrections make the potentials mornmeritun d pe dent and 11amilton's

equal ions must then be used for the trJ j'ctorv cn! rala lions. Our analysis

programs have been considerably extended in scop, in p<<rticull r to make

relativistic analyses and to include much mor< 'xt(n v(. crs' section

information. These programs have the very Islsnt i 1 Lei:FnIion of an lyz ing

the trajectories produced by our dynamical calculations and aso of aver-

aging over an ens em ble of initial nucl ei. W e have aI1 stia rt (d to study

cross sections involving correlation;; b 'twv,'Hc two n111 v 1s.

c. Nonrelativi stick Calculations with Monenluii - 1)-, nt otentiails

A. R. Bodmer and C. N. Pano-s

Momentum-dependent potentials, Whi\:ch involve the solution

of Hamilton's equations, have potentially muc h g re ater flexibility than

static potentials for describing both the scattering and the nuclear r binding

and saturation properties. In particular, to investigate in more detail

finite-range effects of nuclear forces on HE-i collisions, we are con-

sidering momentum-dependent potentials which give the same nucleon-

nucleon scattering cross sections as the (static) potentials used in the

(nonrelativistic) calculations described above (in Sec. VII. E2b). Such

scattering equivalent potentials were obtained by using a canonical t:rans -

formation due to Monahan, Shakin, and Thaler (unpublished).

163

164 VII. E2c

In aiddi tion to giving th si m e sca tte ring, thb nornc nturn -

dclpendert pot-ntials a re also chos-en to give th ( sarn( hindirng energy .s

the original static pOte ntial. Preliminary results for nuclei with A = 20

have been obtained. These resu lt; indicate that the final angular distribu-

tions are quite sirila r even though th<-re re appreciabLe differences in

the porc(ntial energy during the iutera tion of the two nuclei.

VII. Fa

F. MOLECULAR DISSOCIATION AND CHEMICAL REACTIONS

We have continued to develop and improve methods for

treating the multidimensional aspects of the di association of polyatomic

molecules and of chemical reactions.

a. Natural Collision Coordinates for Molecular I)issociation

Y. B. Band and K. F. Freed*

To improve the description of the dyna nii ( s occurring on

the final repulsive surface upon which the fragments recede in molecular

dissociation, we have developed a natural-collisi(fn -cO()ordinate treatment

of these processes. W( introduce a set of conditions to be satisfied by

natural collision coordinates in order to enable the nonseparable, multi-

dimensional bound-continuum Franck-Condon integrals, arising in the

quantum theory of dissociation processes, to he reduced to one-dimensional

integrals. Because these conditions Are not satisfied by available natural-

collision -coordinate schemes, we investigate, in detail, the nature of one

set of coordinates which satisfies these conditions. It is demonstrated that

these coordinates can be chosen to faithfully represent the asymptotic

motions of the fragments as well as the motion of the fragments in the

Franck-Condon region on the repulsive electronic surface. The kinetic

energy operator is C ,played as an explicit function of the repulsive-surface

coordinates, and there is sufficient flexibility in the natural-collision-

coordinate scheme to permit simplifications of this operator if desired.

The half-collision boundary conditions are described in a fashion to enable

numerical computations of the continuum functions alog the reaction

coordinate.

University of Chicago, Chicago, Illinois.

165

VII. Fb, C

b. Distribution of Selected Fragment Vibrations in Polyatomic -Molecule

Di s sociations

Y. B. Band and K. F. Ireed'

We have converted the qua nturn theory of dissocia tion

proce sses (f polyatoric molecules into a form enabling the i sola tion of

selec t l fra grent vibrations. This form ('nables an ('asy (Va liation of the

probability distribution for energy pa rtitioning between this vib ration a nd

all other degrees of freedom that result from the rearrangenent process.

The full quantum theory can, therefore, be viewed as providing both a

rigorous justification for c certain gen (ric: aspects of the simplee golden

ruhe" as we11 as providing a number of irmporta nt geni:ra liz ations thereof.

Some of these involve dealing with initial bound -state vi bra tional xcitition,

explicit molecule, fra gne nt and energy dependence of the effective oscill;tor,

and the incorporation of all isotopic dependence. In certain limiting

situations the full qua ntum theory yields sirnple, r eadily-usa ble analytic

expressions for the fr('quency and equilibrium position of the effective

oscillator. Specific applications are presented for the di rcct photodissoc ia -

tion of HJCN, DCN, 'Ind CC, where comparisons between the full theory

and the sirrple golden rule are presented. We also discuss th' generaliza-

tions of the previous theory to ena ble the incorpo ration of effects of

distortion in the normal rnodes as a function of the reaction coordinate on

the repulsive potential energy surface.

c. Rotational Distributions from Photodissociations

M. D. Morse, K. F. Freed,* and Y. B. Band

A proper description is presented of the bending vibrations

and rotational motions on both the initial bound electronic -state and final

repulsive electronic -state potential-energy surfaces for molecular dissocia-

tion. Analytic expressions are derived for the rotational and orbital

University of Chicago, Chicago, Illinois.

1 66

VII. Fc -- 1

angular momentum distributions of the product s for scalar coupling (as in

predissociations) as well as parallel and perpendicular transitions (as in

direct ohotodissociation). This description makes explicit the separate

and interrelated roles played by angular mInunntum nd energy conserva-

tion. Qualitative agreement with IC N photodi s soc ia ti on ia t a i s obt ained.

d. Franc k-C.ondon Factors for Chem ic al ea actions

Y. B. Band

N ethods for calculating multidiensi 1- ran k- (ondon

transition arnplitudes for chemical reaction> a re ilntrud c((1. " (actiOns

occur ring via various types of surface c rossings a re tr at(2. Single-

surface reactions are reformulated, permitting a Franck-(ondon analysis.

The importance of the topology of the reaction paths and the crossing regions

of the electron-potential surfaces is stressed. The theory is presented in

terms of nuclear natural-collision-coordinate wavefunctions for the potential

surfaces. Analytic methods for deterrnining the continunum -continuum

multidimensional integrals appearing in first order perturbation theory are

presented. Treatment of rotational degrees of freedom is outlined.

Extensions to collisions of a rbitra rily large polyatomic molecules are

discussed.

e. A Physical Parameterization of Density Matrices

G. Gabrielse and Y. B. Band

A general coherently-excited state can be represented by a

density matrix p. When expanded in terms of an angular momentum basis,

the density matrix takes the form

p = Z I aJM)(aJM p a'J'M')(Q'J'M' .aJM, ' J'IM'

No easily-understood and physically-intuitive description of the components

of the density matrix has yet been provided, although such descriptions for

167

VII. Fe

limit(d s u) -blocks of the density ri;itrix do exi st. We introduce an

intuitively-a < essihle pa rameteri nation for the densityy rmatrix in terms of

average values of familiar electric- and magnetic-multipole-moment

operators together with their time deriv;rtive operators. This multipole

moment. and nultipole-rnornent tirne-derivative pictu-re <(an be used to

provide insight into the natllre of coherently -excited states which is

difficult to extract from other pa rarreterizations, such as the above-

mentioned angurla r unor inturrn p;,rarneterization.

W e n;rtu ra lly begin by using the familiar r el e t r i( - ;trnd

magnetic -rultipole operators. Whereas avera ge values of these operators

provide a complete specification of the diagonal d(rnsity -matrix blocks,

there are only enough operators to specify half of the off-diagonal (J J J')

density-matrix elements. An additional set of operators is needed, similar

to the multipole operators except with opposite time-reversal behavior.

We choose to use the tirme-derivative operators of the electric- and

magnetic-multipole operators. The operators are defined as

Zl~r\1I/2 k l': 1Kc1 I /4zrt kq ~ k

Q -Vy* Y ,b O I[ 1, .kg \k + 1k/ kgqk

Our convention for spherical harmonics is that Y are real.

Average values of these operators completely parameterize

the density matrix, and provide additional insight into the physics contained

in the off-diagonal elements.

The utility of using this pa rameterization has been shown in

our work on electron-hydrogen-atom excitation. These parameters are

now under study for ion-atom collisional excitation, charge transfer

reactions, atom-diatomic molecule rotationally inelastic collisions, and

excitation of Rydberg states.

168

VII. Ef

f. EltCt!r(n1 -A\tum1 ((111si ,nl I . t1tiOn

Y 13. Band a ni . Ga hrI lse

W have continltle(d stuldying Vari(1O1s sCatte ring i modes for

el ettrurn -at( Im ()111 is on,11 tx( ittI 1. 111 p, r-tit 111;1r 11'x( i e t g t ll(h '

prt(dictiOns (of the thliri ttitlt m11Odcltl t(r th< oh( r int inultipO1e moIloments

in order to 1.,1rn ai ,lt the t( curacy' of th: , i1 th((lS 1II t rir ting th(

dvna!'c s of th , . P11. Vv( lst ti m ilt lOht -' tuuiitnt pi( turf to gidit

us 111 1pil("t <a l( Ilatt: -',:t mllix '(l--. cUh('rn-i e iuul tio t'> pr( lmO t(d in

;Itomni 1 .'drOg(enI b1 t1 ( t r(I i111 1) ct. W\ ' finld h t ( ('rtai ol thm uch( erenC

mflh)tij)cles ;rt' xtrunmely stnsitivt to the fin1u 1 statt li roo tieiOn b(tweel

scatty ' ci a1n(1 bIaund t(. tronl. A.-, a r. lt, ti Ist -a r(c r-p)(rtu rbttion

scatt-ri ng nl e(- Is ar totaliv rinta 1 I In pr(Ii !]ii! th s 5( i I tip l ts,

tvtin ;t '('r% high enirgis. Tli lOnIgI- ill" 11,11ur (! th (noulomb force

enial ts the dltp; rting( electron to stronLly nix the ntiirly d(gent-rate excited

states, th(reby destroying the lT synumttry of the Born approximations

and rnakiIng pt rturbation calculations unsuitabi *. Therefore we turn to a

clust-coup ing ap)rOximwttionl (C(A) to inllCOrp1Crat( this effect. We use

published 1,-2s-21) H matrices to cailctilate th" low-tnt rgv coherent

iulti )0p1e i (rnments. At higher energi es, where close c onpling R matrices

are expensive to gtnriatt, we have developed classical (CTA) and

quasiclassical (Q(" A) tri jectory a pproximations, which are analogs of the

lower -energy CCA calculations. The coherent rnultipole moments generated

by these approximations extrapolate smoothly to the low-energy CCA

values. These mthods are being applied to electron-atom and ion-atom

collisions.

After comparing our calculations with available experimental

results, we are able to suggest further experiments to fully determine

coherence multipoles.

169

VII. FIg,h

g. 1 << it~t ti( ~ A litudc s f I( r !. < t rIof hrg o t of lk(lr() '(Tr

(G. ; U ri ls rid Y. 1';, ind

W< hi ve ;nri;lyzedI th( ( r tic ,lly the p rud icti<on of (oh er(nt

in fxcit;atiorl of hydro(,eni r r in gfrifrnII ;rnd I p 1)' rtr (1J;t r, for l(< tron-i<

x< it;,tion of the n =2 nd rn < 0tirplfx(s. A rritIltilolf' des( r ption hfs

obttained"( f()r th( ge n(r.,l < ;,s(. whI( 1 < ( 1n (" r ;,t(. t(, physi( ;t y rr,(;tningfu

arid r a sI r;tIble pa ramI tI. ers. 1.1< tron (x< it;,t.i(on no ;,si ur ro m tts of n 3

by Mh;t m et a l. (I1 I1/A) h;v(' b n i na ;m /lyz(d a nd s vera l n w xf r ri tits

proposed t11.( test th( r, ,w 1 d s( ripti(,r. A prin< ilml firling is th(- inat -(c uary,

()f p(-rto rb;ati on cal u IlI;tion s i ob t; i iirni th I (he r''n r c ;giram it-r .

A pr(-f im1tin ary (des( ilpti(on ;h s b (fri pub)li shf (I, ;11( it!n d i fh r 1 pip rs alr

being pr(pa rc (1 fr pubt li< ;ttiun ;Is patrt (A G;. Gfabrlic lsr's P11. 1). th sls.

h. A t ern -IDi tomni c-M ol( ("tublr P(ta ti onally Ar ti d I g icgliso

Y. I,. KI)nd

Thll clis sicf l ((;TA) ;rid ( iiaSiflssi( tI ( (TA) iipproim;i -

lions developed and sl(-(d for tre;ttiig -lictron-itom t ollisions hIav(- been

applied to treat a torn -di;itoniic -rofecii1lc sc;ttt( ring phefnorl-n;. 'o

scatter ring ph(fnonnfroI na ;-re ;t iIIportiinit tool fbr th study, of int( rrmol-cula r

potential s. Ihe .Ibove -mf(lnt.iOncld approxilmations are the atnl og of closf-

coupling a pproximatiun (C CA) m(fthods introduced tf ca lculate rotatiorially -

inelastic atom -diatom collisions, except that the re litive motion is tr 1 -at ed

semiclassic;illy. The computational effort is trem endously reduced from

the CCA -ipproxiration. The Ford-Wheeler semsiclassical. methods are

thereby extended to treat collisions with internal degrees of freedom.

Angular distributions for Ar-HCl are compared with other calculations and

expe r ilm ent.

170

171VII. G ;, I-

fl.. f .1I f I li ' I. 111 ' .,- (

a. :\xiil ( rrtints in >uclei

I -)tfi itt ' I(It I I c I' m St i I IFr ' its Ir t t i I XLI x I \ 'tw k

t te t r hr; tIOt '5 f .( d tt F . iis 1 (' II F! <i t rtlit F t t F s e t t of

t-( txtr ih I ' Ir t fti iy tIw titiv rtIdtI ij l tisl -n i- t rl s ptuti pjov tidtS

n11fJ(t I - in1h(1 tH nii(I t t VI V 11( 5t (1r tilt- t ti Ix< gt < lr I n . e h}l e hi ow I

thit ( l rn111( >t i r i lt' t -; t ig n fr ; tF ( 'i L H t ti t bii hi (' in g

\11 ;xpi) I( t tw<(1-bUlody ,~ <> <r'tor' r<-pr<-s I tIin tI s t'ftfe t has b<- I gIV n i n 11 a

171(thI I-Ind t'pt'ndt' t w );I b St.( ('1 thlt ](V ltw .. Ir V lft ( <>r 'f . 'I het im porUItaC-t1

('0n111" ti n wit h t stin g ouir r, Iets.

Institut dt I'h ysiqpue Nll( 1 lire, Unive rsit( C11.udt iWrna rd, 69621,Vill(urbanii, rance.

St 'rvice cit Ilh sii ihf(ericI, CIN SnK'lay, 91 190 Gif-sur-Yvette,F ran .

h. ';ne rgv i)tpend( nt ft Value and 13(M 1) in Be

K. Kubocr;i afnd T. Tornoda

The (3 and the y (decays involving the A=8 nuclear systems

have recently been studied in great detail with the view to testing CVC

and/or the possible existence of second-class currents. To interpret

these experiments, it is important to understand the structure of the first

excited 2 state in 8Be. An intriguing feature established recently is that

the line shape of this level differs appreciably depending on whether it is

fed via P or y transitions. In order to explain this remarkable feature,

we have made a microscopic structure calculation for the continuum 8Be

state based on the extended cluster model, and we have- calculated the ft

University of Tokyo, Tokyo, Japan.

VII. Gb-d

value and B(M 1) value as functions of the excitation energy of the final state.

The difference between the line shapes is semiquantitatively reproduc ed.

c. Polarization in Nuclear Reactions Involving Photons

R. J. Holt, R. M. Laszewski, and J. E. Monahan

The extension of the S-matrix formalism to include photons

depends essentially on the transformation of S-matrix elements to a

representation that describes photon channels. Derivations of this tratnsfor-

rnation given in the literature contain an ambiguity. Specifically, the

relative phase of the vector potentials for th I electric and1 ma gnetic

2 -pole fields is not uniquely defined. The condition that thes pote ntia ls

transform as do the corresponding pa rtic l a ngula r momentum eigenfunctions

under time reversal reduces the phase ambiguity to one of relative sign.

The (arbitrary) choice of this sign rmnist be specified in order that the

relevant S-matrix element be defi ned uniquely. Failure to take these

additional conditions into account may be the cause of recent discrepancies

in the analysis of photonuclear polarization data.

d. Nuclear Mass Relations and Equations

J. E. Monahan and F. J. D. Serduke

Relations among the masses of neighboring nuclei provide

an accurate and convenient method for the estimation of unknown mass

values. A set of such relations has been "derived" and their structure as

partial difference equations has been investigated.1 The result is a set

of mass equations (solutions of difference equations) that can be ordered

so that each successive member is potentially a more nearly accurate

representation of nuclear ground-state energies. The first two members

of the ordered set are the original Garvey-Kelson mass equations. The

third member of the set, fitted to the known masses, satisfies the principle

J. E. Monahan and F. J. D. Serduke, Phys. Rev. C 17, 1196 (1978).

172

VII. Gd,e

of charge symmetry to a significantly better approximation than do the

first members of the set. As a consequence, it is expected that reasonably

accurate predictions, particularly for the masses of proton-rich nuclei,

can be obtained from this third equation.

e. Isospin Restrictions upon Chargt Distributions in Charmed Particle

Decays

Murray Peshkin and Jonathan L. Rosner*

The calculations described last year hive been completed and

published in Nuclear Physics B. Isospin invariance implies certain re-

strictions upon the charge distributions in each decay mode. We calculated

the tightest possible bounds for various functions of the charge distribution

(neutral fraction, fraction of events which allows one-constraint or four-

constraint fits, etc. ) in the known decay modes of the known cha rmed

particles. We also introduced joint bounds on two such functions of the

charge distribution.

173

175

EXPERIMENTAL ATOMIC AND MOLECULAR PHYSICS RESEARCH

INTR0DUCT10N

The (xpe riim-enta l research program in atomic and

molecular physics consists of eight research projects as follows:

A. Dissociation and Other Inte reactions of Energetic Molecular Ionsin Solid and Gas eouis Tar gets (I). S. Gemm ell)

B. Beam -Foil P esta rch and Coltlision Dynami( s of Heavy Ions (H. G.

Berry)

C. Interaction of Em rgetic Pa rticcs with Solids (M. S. Kam insky,S. K. Das)

1). Ihotoionization-Photoelectron Resea rch (J. B3e rkowitz, J. H. D.

Eland)

E. High-Resolution Spectroscopy of Atomic Beams with Tunable Lasers

and Radiofrequency Techniques (W. J. Childs, L. S. Goodman)

F. Mossbauer-Exfect Research (G. J. Perlow)

G. Monochromatic X-Ray Beam Project (S. L. Ruby)

H. Scanning Secondary-Ion Microprobe (G. R. Ringo, V. E. Krohn)

The first three are based on the use of our nuclear accelerators.

VIII.A

VIII EXPERIMENTAL ATOMIC AND MOLECULAR PHYSICS

A. DISSOCIATION AND OTHER INTERACTIONS OF ENERGEIC

MOLECULAR IONS IN SOLID AND GASEOIhS TARGETS

The Argonne . -MV Dynamitron a c ccl rator is used to

study the dissociation and other interactions of fast (0. 3-4.0-MeV)

molecular ions incident upon thin (~ 100 A) foils and gaseous targets.

Molecular-ion species employed thus far ra nge from H2' ut to Ar" 11.

A unique feature of the appa ratus is that it permits exceptionally high -

resolution (,0.0050 and X300 eV) measurements of the distributions in

angle and energy for particles emerging downstream from the target.

The work has two major objectives: (a) a general study

of the interactions of fast charged particles with matter, but with the

emphasis on those aspects that take advantage of the unique features

inherent in employing molecular -ion beams (e. g., the feature that each

molecular ion incident upon a solid target forms a tight cluster of atomic

ions that remain correlated in space and time as they progress through

the target) and (b) a study of the structures of the molecular ions that

constitute the incident beams. Precise measurements u.i the energies and

angles of the breakup fragments produced when fast molecular ionsdissociate in foils and gases offer exciting possibilities as a new method

for determining molecular -ion structures.

These two aspects of the work are mutually interdependent.

In order to derive structure information about a given molecular ion,one needs to know details about the way the dissociation fragments collec-

tively interact with the target in which the dissociation occurs. Similarly,a knowledge of the structure of the incident molecular ions is important

in understanding the physics of their interactions with the target. We have

therefore begun our work with careful studies involving beams of the

simplest and relatively well understood diatomic molecular ions (H +HeH'+, etc.). Even with these, several new and inte resting phenomena

have been encountered (e. g. , the interactions between the molecular

constituents and the polarization oscillations that they induce in a solidtarget; the marked differences in dissociations induced in gases ascompared with those in foils; the anomalously high transmission of some

molecular ions through foils and the appa rent absence of any transmission

in other cases). As our understanding of these phenomena develops, weare going on to studies involving more complex projectiles.

177

VIII. Aa

a. Dissociation of Fast HeH Ions in Foils and Gases

D. S. Gemmell, FP. J. Cooney, W. J. Pietsch, A. J. Ratkowski,and Z. Vager

In an effort to gain a thorough understanding of phenomena

observed when very simple light diatomic ions are incident at high

velocities (v v0 , where vo = e 2/h) upon thin foils and gaseous targets,

we have performed an (xteasive set of measurements upon the dissociation

products arising from be:tms of HeH , e.g., Fig. 41(a). In these

measurements we have varied such parameters as the beam velocity, the

target thickness and composition, and the

molecular-ion beams (3HeH1 and 4HeH ).

isotopic composition of the

In addition we have obtained

17

Iy

(a)

I __

I '

Fig. 41. (a) Experimental and (b) calculated joint distributions in energyand angle for protons emerging (near the beam direction) from an 85-A

carbon foil bomba rded by 2.0-MeV HeH+ ions. In the experimentally

determined distribution there are about 10,000 proton counts at the maxi-

mum. In the calculations, the hydrogen ions are assumed to be singly

charged both inside the target foil and after leaving it. The helium ions

are assumed to be doubly charged inside the foil and 92% doubly and 8%singly charged after emergence from the foil. The two single-parameter

spectra shown in both (a) and (b) are the distributions for zero shift inenergy and angle. They thus correspond to cuts through the center of

each two -pa rarneter distribution.

178

091.

i

VIII. Aa,b

data for a variety of charge states of the dissociation products (H , H 0 , H ,

He , He , and He ). The large quantity of experimental data acquir-d

for these HeH beams is now-being analyzed with a view to testing and

refining in detail the theoretical model we recently developed to take into

account the influence of effects such as polarization "wakes," multiple

scattering, etc. in foil targets. 'lhe experimental results obtained for

the variously-charged dissociation fragments are proving to be of con-

siderable interest. The data show clearly that for H0 and He+, the

electron pickup probability is a maximum at the exit surface of the

target foil. But for the 2-electron systems H and He0 , the situation is

not nearly so clear-cut, and further work is needed to determine how

these charge states are produced.

Preliminary work with crude gas targets (obtained by

flooding the present target chamber with gas) shows the strikingly different

behaviors to be found for dissociations in gases and solids. The energy

spectra for the breakup fragments from gases are symmetric (no wake

effects) and favor lower charge states.

b. Dissociation of Other Diatomic Molecular Ions

D. S. Gemmell, P. J. Cooney, W. J. Pietsch, A. J. Ratkowski, andZ. V;iger

In addition to the work on HeH , we have made similar

but much less extensive studies of the dissociatio of beams of H-1 , CH ,

OH , ArH , He 2 , NL+, CO+, and 02+. The results indicate (rather

surprisingly) that the molecular ions are almost always incident on the

target in their ground electronic and vibrational states. For the heavier

molecular ions, refinements to our theoretical model seem to be needed

in order to account for some aspects of the data. Several new and inter-

esting phenomena have been observed: e.g., the H0 fragments from 3. 7-

MeV OH bombarding a 185-A carbon foil appear to originate mostly from

protons that pick up an electron about 100 A downstream from the target;

M7

VIII. Ab, c

the proton energy spectrum observed for 2. 8-MeV OH+ dissociating in a

gas is symmetric and displays beautifully several peaks corresponding to

the oxygen fragments being left in charge states 0, 1, 2, 3, and 4.

c. Theoretical Model for Dissociation of Fast Molecular Ions in Foils

D. S. Gemmell, E. P. Kanter, and Z. Vager

We have developed a theoretical description of the polari-

zation wake induced in a solid by the passage of a fast charged particle

(Fig. 42). The model uses the formalism of the macrosropic frequency-

dependent dielectric function. The effects of close electronic collisions

are taken into account in a semiclassical fashion by extending the thickness

of the classically-catlculated polarization-charge distribution by an amount

~h/mv, where m is the electron mass and v is the projectile velocity.

The resultant potential distribution correctly accounts for the electronic

stopping power of the medium. Calculations based on this model give good

agreement with the results of our experiments on the dissociation of

fast molecular-ion beams [Fig. 41 (b)]. The model is presently being

extended to take into account in a detailed way the correct form of the

wave functions for the individual states of the incident molecular ions.

SFig. 42. Potential distributionassociated with the polarization

t vei carbo = wake of a 400-keV proton- - - traversing carbon (np =25. 0

eV). Distances are shown in

units of = 2-7a = 14. 5 A.

0.0 0.

180

VIII. Ad

d. Transmission of Molecular Ions Through Foils

D. S. Gemmell, P. J. Cooney, E. P. Kanter, W. J. Pietsch, A. J.

Ratkowski, and Z. Vager

When fast molecular ions are incident upon a thin foil

target, the re is a small but definite probability (typically in the range

~01- to 10 -3) that the ions will be transmitted through the foil. We have

studied this phenomenon, measuring the transmission probability, the

energy loss, and the angular distribution for many different beam species,

beam energies, target thicknesses, and target materials. We have

+ H+ + 3 + 4 + +observed transmission for H+, H3+, D3+, HeH , HeH , and OH.

However, for 4-MeV 0 and 2-MeV CO incident on thin C foils, the2 -11

transmission probability was too small (<10 ) to observe. We find

large variations in the transmission probability depending upon the target

rnaterial-e. g., by switching from a carbon target to an Al2 3 target of

the same thickness, the transmission of H2 goes up a factor of 10.

Although the physical origins of the transmission are still unclear, we

have made some progress in understanding the phenomenon. Our results

on the energy losses, straggling and angular distributions indicate that

those molecular ions that are t transmitted act like single projectiles in

their passage through the foil (and not as Coulomb exploding clusters).

We have demonstrated that channeling (e. g. , in the polycrystalline

structures of some targets), multiple scattering and quantum mechanical

effects ("borrowing" energy from the Coulomb explosion for short times)

are not responsible for the transmission. For the extensive data on 41lel+

transmitted through carbon, we have been able to find a function P(r),

where - is the dwell time in the target, such that the transmission

probability can be written T = P(r) exp (-v). Here v is the beam velocity.

We interpret P(T) as the probability that the molecular constituents can

maintain a state for a time - in the target, such that recombination at the

exit surface is possible [with a probability oc exp (-v)].

1 81

VIII. Ae

e. Determination of Molecular-Ion Structures

1. S. Gemmell, F. P. Kanter, and W. J. Pietsch

The development of high-resolution techniques for studying

the foil dissociation of fast molecular-ion beams, coupled with our

improved understanding of the physical processes involved in the inter-

actions of the resulting clusters with foil targets, now opens up new and

exciting possibilities for the investigation of the structure of molecular

ions.

(,) H1 +. Although H is one of the simplest molecular3 3

ions, its structure has not previously been determined experimentally.

Our measurements on the foil dissociation of fast H beams have for3

the first time demonstrated that in the ground state the three protons

form an equilateral triangle whose dimensions and vibrational motions

are iii good agreement with calculated values.

(b) CO2 and N20+. By measuring energy spectra for the

variously charged monatomic fragments that emerge in the beam direction

when 3. 5-MeV CO and N20 beams dissociate in thin carbon foils, we

have demonstrated that CO2+ and N20+ are linear with the structures

(O-C-O) and (N-N-O), respectively. Although these structures were

previously known, we measured them to demonstrate the power of this

new method-the gross features of the structures are easily deduced even

from a casual inspection of the energy spectra for one set of charge

states. Details of the structures (precise bond lengths and angles, together

with information on the vibrational motions) can be extracted from the

results of these measurements, if we are able to extend our computer

calculations (which successfully account for results obtained for light

diatomic ions) so that they are valid for the more complex cases involving

polyatomic heavy molecular ions. Work on these calculations is in

progre-s. Structural details can also be determined more precisely

with the aid of coincidence measurements and we are in the process of

setting up for this type of measurement.

182

VIII. Ba

B. BEAM-FOIL RESEARCH AND COLLISION DYNAMICSOF HEAVY IONS

This research program is aimed at develo .- , a coipre-

hensive understanding of multiply-ionized heavy ions: on thu one hand, their

atomic parameters such as the energy levels and radiative lifetimes,and on the other hand, their production, de-excitation and re-excitation

by collisions in gases, solids and at surfaces. One aspect of this study

is to explore the systematic variation in the energy of x-ray resonance

radiation and fluorescence at lower energies (the vacuum-ultraviolet

region). This information will also be valuable as a diagnostic tool in

the analysis of thermonuclear plasmas. We hope to demonstrate which of

the various decay channels for an excited, multiply-charged ion are most

easily detectable and distinguishable from those of other species.

Atomic-structure measurements in two- and three-electron

ions are continuing in tests of basic calculations of relativistic and radia-

tive corrections in atoms. The most stringent tests are in the quantum

electrodynamics (Q. E. D.) of high-Z two-electron ions.

A general goal is the understanding of the collision processesof fast heavy ions passing through solids and gases. We analy. the re-

sults of such interactions through observations of the photons emitted

from ionic excited states. Scattering amplitudes and cross sections are

determined from intensity and polarization measurements of the light

yield. The interactions with solids necessarily fall into two parts-

surface and bulk interactions. 'wo types of comparative measurements

are thus made: surface scattering of fast ion beams and tilted thin-foil

excitation of the same ion beams.

The experiments are carried out at the two Physics Division

accelerators, the 4-MV Dynamitron and the Tandem, which provide avariety of ions at energies from 1 MeV up to about 70 MeV.

Collaboration with theoretical physicists at Argonne andelsewhere has been initiated for the interpretation of both tihe collisionphenomena and the observed atomic transitions.

a. Orientation and Alignment of Fast Ions by Thin Tilted Foils

H. G. Berry, A. E. Livingston, G. Gabrielse, and T. Gay

A thin carbon foil, with its surface tilted to the fast beam

direction, induces both orientation ar.d alignment of excited atomic states

183

VIII. Ba--c

which are measured by the polarization fractions of the light emitted in

radiative decays.

We have measured the dependence of alignment production

by thin foils perpendicular to the incident ion beam on the foil material

(e. g., conductors C, Au, and Ag and nonconductors SiO 2 and W2 3)'

Large variations are observed both with material and with time as carbon

deposits build up on the back surface of the foil. The alignment also

varies with incident ion-beam current density and foil temperature. These

two effects are be,, eved to be related and further investigations are con-

tinuing both experimentally and theoretically to understand the interaction

mechanism.

b. Orientation and Alignment of Fast Ions by Grazing Collisions with

Surfaces

H. G. Berry, A. E. Livingston, G. Gabrielse, and T. Gay

Fast ions incident on surfaces at grazing angles of 100 or

less produce a strong forward-scattered component close to the specular

direction. Electronic interactions as the ions leave the surface create

strong atomic polarized light emitted from excited states of the moving

ions. From measurements mainly on Ar ions at incident energies of

about 1 MeV, we have proposed a theoretical model of the interaction

process. The initial work has been published. Further experiments to

compare alignment and orientation production from solid surface scatter-

ing and thin foil transmission are being analyzed, and the work is con-

tinuing.

c. Electric-Field Quantum Beats

H. G. Berry and G. Gabrielse

Foil excitation of hydrogen creates coherence of opposite

parity states (e. g., 2s-2p states) which can be measured as a change in

phase of the Lamb shift quantum beat when a longitudinal electric field is

184

VIII. Bc,d 8

reversed in sign. We have extended and improved the accuracy of our

initial measurements with an automated field reversal technique. The

data analysis now in progress gives the absolute cross sections for 2

and 2 p as well as the s-p and p-p coherence terms over a proton-energy

range r f 0.02 to 1.5 MeV.

d. Grazing Incidence Spectra and Lifetimes

H. G. Berry, J. Desesquelles, and R. M. Schectman

The Ne I-like resonance doublets of Cl VIII and Ar IX

near 58 A and 49 A have been resolved, and their decay times measured.

The mean lives have been compared with other measurements of lower

members in this isoelectronic

sequence and with a number of .x

recent configuration -inter ac tion _ C.20 -

calculations. The results are -015."ix ----KASTNERet a.(H.F)

shown in Fig. 43. 4x -+-CRANCE (P.P)

With the help of

relativistic Dirac -Hartree-Fock

calculations by K. T. Cheng (RER

Division, ANL), we have identified

a group of partially resolved

satellite lines about 10 A above

the Ne I-like resonance lines. We

have partially resolved these

satellites which are inner-shell

excitations of the Na I-like ions.

o _j .. IREL. HF. THIS WORKo BFS THIS WORK0 BFS. CURNUTTE etal.+ AYMAR et ol.

a 0.05 A REL RPA SCORER---

Co Ar CI P Al No Nen XIX ID M VM III II I

0.05 0.06 0.07 0.08 0.09 0.10

0.08

00.06W

-

a04

0

0

X

-\x\

-- i

0.05 mn~nm 0. m 00.05 0.06 0.07 0.08 0.09 0.10

Fig. 43. Absorption oscillatorstrengths for the iS - 1P (upper)

and iS - 3 P (lower) Ne I-like reson-ance transitions as functions of

inverse nuclear charge t/Z.

'1

185

VIII. Be -g

e. X-Ray Spectroscopy

H. G. Berry, A. E. Livingston, and W. J. Ray

The resonance transitions of the more highly-stripped ions

occur in the soft to medium x-ray region. A curved-crystal high-resolu-

tion monochromator has been acquired for studies of these species. A

specially designed target chamber with time resolution expected to be

about 1 ps for Tandem-energy beams has been coupled to the mono-

chromator. This will allow simultaneous observations of x rays (1-40 A)

and grazing-incidence photons (30-500 A) with the possibility of coincidence

measurements.

f. Doubly-Excited States of 3-Electron Ions

A. E. Livingston and H. G. Berry

We have observed the 2s2p 4P -2 4P transitions in

C, N, and 0 with linewidths of 0.25 A near 1000 A. The resolution was

sufficient to resolve their fine structures for the first time to provide

tests of several different calculations of the magnetic interactions of

3--electron ions. All presently known calculations are shown to be in-

adequate in predicting the level separations and K. T. Cheng (RER

Division, ANL) is attempting an accurate relativistic calculation.

Different decay times for the fine-structure components also show that

autoionization rates are important for some of the components.

Analysis of C, N, and 0 beam-foil spectra is continuing to

identify higher-lying levels in the doubly-excited quartet systems of the

Li I-like ions.

g. Cascade Analysis of Beam-Foil Decay-Time Measurements

H. G. Berry, R. M. Schectman, A. E. Livingston, and G. Gabrielse

Cascading is a primary problem in obtaining precise atomic

mean lives from beam-foil intensity-decay data.

1 86

VIII. Bg-i

We have investigated the capability of a mathematical

technique comparable to a coincidence , measurement between photons of

cascade transitions and the transitions to be measured. A system of

successive feeding transitions in O II was measured. Preliminary results

show that accuracies of the order of 1% can be achieved, equivalent to the

most accurate mean life measure ants. The signal, compared with direct

photon-coincidence measurements, --inced by at least a factor of 106.

h. Foil Breakage under Heavy-Ion Boy, .,ardment

H. G. Berry, A. E. Livingston, and G. E. Thomas

We have verified that foil lifetime under heavy-ion

bombardment is independent of the foil thickness for carbon thicknesses of-2 -2

2 g cm to 25 g cm . Foils of different diameter and beams of

different cross sections (3 to 7 mm and i to 5 mn diameter, respectively)

also showed no variation of lifetime. We used Ar+ ions of 1 to 3-MeV

energy and Ni ions of 3-MeV energy and beam current densities of

1 to 10 A cm-2. The lifetime was a function of the total ion dosage,

independent of beam-current density.

i. Optical Observations of Molecular Dissociation in Thin Foils

H. G. Berry, A. E. Livingston, and G. Gabrielse

By observing photons emitted along the beam direction we

have reduced the Doppler broadening normally present in beam-foil spectra

at visible wavelengths by a factor of about 5, obtaining linewidths of less

than 1 A at 5000 A.

An initial test of this system was a measure of the molecular

dissociation energy of molecules such as (N H ) and (O H ) , wheren nn = 1, 2, 3 when they break up inside the foil through observation of the

light subsequently emitted by excited neutral hydrogen. Our observations

show clearly the effects of the "wake potential" on the dissociation energy

187

188 VIII. Bi

(a)FRONT

CARBON SURFACEFOIL MIRROR

(XHn) /

100 0FARADAY5 CUP

COLLECTIONLENS

(F= Ocm)

SPECTRE

1200

IOGO -

800-

600 -

400

200 --

(b) <Q*

_ rn)

11

7c1-

q

s/2

0.91,

1ztr _ -A' -4766 4768 4770 47/4 4776

DOPPLER-SHIFTED WAVELENGTH (x)

Fig. 44. (a) The experimental

arrangement for observation of

spectral lines with small Doppler

widths. (b) A N III tripletresolved

break up

from Ba @ after foilof NH+

as an asymmetric profile of the emitted spectrum. Results of measure-

ments on Balmer P are shown in Fig. 44. The small halfwidth of the

N III triplet contrasts with the broad 3a-P line. A preliminary paper

has been published and further analysis of the data is in pro ress.

z00

oacr)ti

VIII.C

C. INTERACTION OF ENERGETIC PARTICLES WITH SOLIDS

The overall purpose of this research project is to study

specific atomic and molecular phenomena that occur when energetic

ions (keV-MeV range) interact with both bell, and surfaces of solids.

Particularly, fundamental studies of the mechanisms underlying (a) the

release of atomic and molecular species from solid surfaces, and (b) the

changes in the surface topography and in the mic rostructure of the implant

region under energetic -particle impact are being conducted. One main

goal of these studies is to determine experimentally how incident particles

which become trapped in the lattice can influence (1) particle release

yields, (2) the type of species released, and (3) the energy loss of the

incident ions within the implant region through processes affecting the

propagation of atomic collision sequences in surface regions, and the

surface binding energy. For example, certain types of trapped ions(e. g., H, 1), He in metals) may precipitate out If solution and form

(in the presence of voids), bubbles in the implant region of the lattice.

A high density of gas bubbles in this lattice region <an hinder the

propagation of recoil atom collision cascades in that region and may

represent a "quasi-gas target region" within the solid. Existing theories

for particle release by physical sputtering (e. g., P. Sigmund, W. Brandt)

and for the stopping of ions in solids (e. g. , Bohr, Lindhard-Scharff,Brice) neglect the role of the trapped incident projectile. The experimental

results will be compared with predictions made from existing theoriesfor particle release and will be used for the development of new models.

These types of studies are also of importance for the identification of some

ol the major effects which contribute to plasma contaminant release and

surface damage and erosion of certain components in plasma devices and

future fusion reactors. With a better understanding of the basic mecha-

nisms underlying both plasma contaminant release and surface erosion,the development of solutions for their control will become meaningful.

Furthermore, experiments will be designed for a search

of molecular ions formed b the simultaneous interaction of two independention beams (e. g., H+ and D in the 10-keV-100-keV range) with solid films(both transmission and backscattering experiments -use of nonocrystalline

and polycrystalline films).

The experiments are carried out with well-characterized

surfaces of solids (scanning electron microscopy, transmission electronmicroscopy, and scanning Auger spectroscopy). The irradiations will becarried out with three different facilities. One facility is a recentlycompleted (1977) novel accelerator system which produces two ion beamssimultaneously, and merges them on the same beam axis before permittingthem to interact with solid targets (angle of incidence is then a free

189

VIII. Ca

armeter). This system allows in situ sputtering yield determinationUnder o ltr;thig}h va uun conditions. It a so allows a search for the forra-

tion, of molecula r speci e formed by the sirnult;ineous inte ra< tion of ionsof two rdiffe rent species ((. g., II+, I)+) with solids, and ;ilso ; search for

inter;,( tive surface effects on the release of ta rget pa rticles and on t a rget

surf;, e damage and erosion. The second facility consi sts of a low-energyion ;, < ler.,tor (1 keV to 15 keV) whi< h will be ;tt; hed to an existings5 ;nning Auger spectrometer (luring 1978. This system allowss in sito

determlin;ition for low ion energies under oltr;high-vacuurn conditions.(;;librt(d splitte'r-depth profiling will 1 be used to determine the sputter(h-posits il situ. The third facility, upgraded drying 1977, produ( ed

high < ir rent densities of nass analyzed ions (,1() mA/cm 2 ) in the 10-keV

to 120-keV energy range a nd willow'ss ta rget irr;,diation in the olt rahigh-

v;ic n m r;ngi.

(orrelation of lihster I)i;,rmeter ,Ind skin Thicknes and the M.. hInism

of 1 listede r I" ornIit ion

S. 1. l)as, M. Kaminsky, and G. 1e rsk

Different m od, k h; vIE bcen proposed to (>li ; in thi e fortm);,tion

of sorfa, e [A istc rs on heliun -boImb; rded su rla ces. Soch lmodels r,

h;sed un (a) gas-bubbh1 co;ilescen e a;nd the boild op of lit( r,,l gds

pressure, Or (b) the percolation Of heliiumn in tw lattict, ;Ind/or (c) th.

buildup of strc ss ts in the irnpl;inte d layer. Some mOdlc s of the Iatter

type strgge st that la rge lateratl strEsses lit reod(Iced in an ion-imtplainte(

surface Ltyer nr;iiy c(mse elstic inst;bility alnd bulc(kling of thl implant

l;Iver, ;Inl result in a relationship 1 ( t S between the most probe ; blt

blister dimtnieter ') and the listed r skin thih kness t for metals su(n asmy

Be, V, stainless steel, Nb and Mo. 1(o test this relationship a systematic

study of the c((4rrelati 41 between blisteri di;,meter ;tnd skin thickness for

helium blistcrinm of ;tnnealed tool"c rysta Ili ne and mlonoc r stalling V (100)

su rf;i ces has been cm jnplet ed for the energy range of 20-500 ke V.

For the monoc rystalline V (100) surface, one obtains the relationship0. 91i) -= 7. ' , whereas for annealed polycrystalline V, the relationship

is 1) = 6. 3 t . These relationships do not support the lateral stressmp

model for blister formation, which predicts the generalized relbtionship1.5

D) x t for manisy ma.te rials. Experiments are in prog res s for an fcc

1 90

VIII. Ca, b

m metal \ , t; h< 1 m tI ;t, 1int I ( til b. 4) ports bas d on part s

of these Studies %vill ;t 1)pp t r in J. .i)I) . I)}1 .

b. )( - th ) istribti in >f :! litrin i',u!) lt s il n i( k i

G. F- nskt, S. 1K. 1).s, id 2. K1 1.it s K'

y tt mt ti < .s( t(1(1 , V.( y 1mt ia<, d 1a .1 e ti . ' 1 (I('t'1'r liin , tht'

'ff(ct <If (1hem11 ( llV- tiv (r.Lg., iti'.dr'(t't: t tl s) < ir i < (t (, . , l ')

rtLg(iens. I li< ;!nrar IIO:l ol thi:- t , Iri Ii IVi , l- i II

< hingts ill 1 t - s r ft( rt i (gi ,I ,i l t 1. ) +r 1, 1 : 4 ,V r ninl th le p r-

ti lI re1( ; se ((. g. , 111 rf; t" A ridith , r gv , tIl h 10 ', i 1tpu)nt nt )f ((-lilsion

iat sr d(ls). IlrtirIIarl\', strii.- on ti- <1 :tL It.tibtioni I bubleS amnd

1"r S il jO l- I r;t1 i itk 1(I t l i II i, ti r I i I I t Ii )II i 1)tI) li ;I ng idV(,i( - 111 1i fn -Irrai1 tt( mtll.1 s ;1'' re t <>f (i , I'1 11, i0 t Io In I n11h rstand(1ing Of

th I m re ha1nismls of r-rldi :ticn r i st ri .II

Thr silti , nrirIin t b F (hi11- its 1 1'd v<>ltrr fr;, tion of (a viti Os

( .g. , voids a nd bubble s) in ii,. k(lI irr ;,dit(ld "t SOt(J ( .th 5()-k V ;nd

2O-ktV I ions h Itvt ( bj n ;tur(A ; s i fun( ti(nt ()f (t 1)th from tht

irrai(iate(d snirf;< ( for ttattl jdos s just bUlow tht ( ritit I (lOst for blister18 2

app1)';tran<( (( 14 g , 1 10 ions/< m1 f')1 5llO-k('V ;Ind i - 10t ions/cm

for 20-keV .1 ions). The depth (listributlo11 \%I- (Abt;tin1(d by- trauisiission

electron mi ros( opi( studlits of sanipts tc'tihn(d p rilbI t<t th. direction

of tht ir.( idezit )eamn.

Figure 45(a) shows a typicil bright-fit Id transmission

cIc tron m icrograph (T EM) of the plated aInd irra di;tted regions (the inter -

face between the two is ma rked by a r rosvs) of the 500 -ktV i r radiated

sample. The swelling (AV/V) due to the cavities (voids or bubbles) was

measured from enlarged micrographs as a function of depth at 500 A

intervals and is shown in Fig. 45(b). The solid and dashed curves show

the depth distribution of energy deposited into damage, and the projected

191

VIII. Cb

,4

DAVMA(JA

FHl (. FEL

GIPIj1. ~ N d

[A PTH (1sm)

i4 c.

,

rrI

2 a,I(.

11 rr(.w

.J

V1

" o Cr

Ir c

'I f

w

r4,

rrU a

Fig. 45. (a) Bright field T EM of

annealed polycrystalline Ni

irradiated at 500 0 C with 500-

keV 4He+ for a dose of 5 X 10 1 7

ions/cm 2 . (b) Histogram show-

ing swelling (OV/V) as a func-

tion of depth from the irradiated

surface for the micrograph

shown in (a).

z

U-

U.

-J0

'5

IAIIID

0

H

020.1 0.2 0.3

DEPTH (rm)

-4

8

6

J

0

zC)wr

U

a

SURFACE LOCATIONI) UNCERTAINTY

Fig. 46. (a) Bright field TEM of

annealed polycrystalline Niirradiated at 5000C with 20 -keV4 He+ for a (1(se of 2.9 ;< 1017

ions/cm 2 . (b) Histogram show-

ing swelling as a function ofdepth from the irradiated sur-

face for the micrograph shown

in (a).

Irange calculated according to Brice, respectively. Also, the experimen-

tally measured blister-skin thickness is plotted with the error bars. It

can be seen that the peak in the swelling agrees well with the peak in the

projected range distribution and with the blister-skin thickness. The

cavities seen at the interface and in the plating are probably due to trapped

hydrogen bubbles generated in the nickel strike solution.

Figure 4 6 (a) shows a bright field of TEM of the 20-keV

irradiated sample and the corresponding histogram of the swelling as a

tR. Behrisch, M. Risch, J. Roth, and B. M. Scherzer, Proceedings ofthe 9th Symposium of Fusion Technology (Pergamon, 1976), p. 531.

192

I-Cr

-

b

- ~

I -1F

'. .

Jr.

VIII. Cb, c

function of depth is shown in Fig. 46(b). The dashd curve represents the

calculated projected -rang- probability distribution. The mnta surcd blister-

skin thickness is shown by the horizontal I ha r. I Ietre it can be seen that

the depth at which the swelling peak occurs is at a much la rge r depth than

the peak in the calculated projected-r nge distribution, but atr. es w(l

with the blister-skin thickness. Ihese results suggest that the sepi ration

of blister skin occurs at a depth where the volume fra.otion of tih heliom

bubbles is at a naxinmurn. The critical dose for blijter f rm aticun is

reac hed when interbubble fracture has been initit d m th, r gion of

ma xirnurr swelling wh ( re the interbubble dist anc h-s be On st!ffic ie(ntly

sm;,l. Reports based on these studies will appea r in the Joirnia I of Nuclca r

Materials and in Transactions of the American No lear >m it t . Detailed

stulies on the effect of total dose and of i rradiationi t emipe ratI r. on the

deptf; distribution of si z 0, density, and volunie f ra tion of bIbblcs a re

in progress.

c. 'ntera cti ve ffe cts on Surface Damlgc D ult to Sinuilttnt-ous I1-rradiation

of Ni with J)+ arid le

M. Kaminsky, S. K. Das, R. Ekern, and 1). C. hless

These experiments are aimed at sea rching fo r inte ra eti vt

effects on surface damage and erosion due to sinultanutous bombardnent

of m'tal surfaces with D+ and He . As a test case, nickel was bomba rded

at 5000 C with 50-keV D+ and 100-keV He+. 1)r these t%%o projtctile

energies, the projected-range distribution and the depth distribution of

ener y deposited into damage are similar. In order to see whether the

surfs ce damage observed during simultaneous irradiation is an inte active

effect or not, five sets of irradiations were performed; two separate

irradiations with two individual components, sequential ir radiation with

50 -keV D and then 100 -keV He , another sequential irradiation with

reversed order (i.e., first 100-keV He+ and then 50-keV )+ irradiation)

and finally, simultaneous irradiation with 50 -keV 1)+ and 100 -ke V He+ ions.

1 93

194 VIII. Cc

'*11

Fig. 47. Scanning electron micrographs of anncalt d polycrystalline nickel

irradiated at 500 0 C (a) with 50-keV D+ to a dose of 0. 5 C/cm 2 , (b) with100-keV 4 He+ to a dose of 0. 1 C/cm 2 , (c) simultaneously with 100-keV4 He+ and 50-keV D+ to total doses of 0. 1 ind 0. 5 C/cm 2 , respectively,(d) sequentially with 50-keV D+ to a dose of 0. 5 C/cm 2 , and then with100-keV +He to a dose of 0. 1 C/cm 2 , and (e) sequentially with 100-keV4 He+ to a dose of 0. 1 C/cm 2 and then with 50-keV D to a dose of 0. 5

C/cm 2 .

Initially, total doses were 0. 5 C/cm2 and 0. 1 C/cm2 for 50-keV D+ and

100-keV D+ ion irradiation, respectively. For the single irradiations with

D+ and He+, no detectable changes on the surface were observed [Fig. 47(a)

and (b)]. For the simultaneous irradiation with D and He+ ions, blisters

with densities ranging from 1.5 X 104 to 9.4 X 105 blisters/cm2 were

observed [Fig. 47(c)1. Blisters were also observed for the two sequential

VIII. Cc,d

irradiations [Figs. 47(d) awd 17 (e)] , but their densities were lower

(1 X 10 - I X 105 blisters/rm2 ) th:1 n the simultaneous irradiation case.

However, when the total dose for 100-keV He+ irradiation was increased

2 +to 0.2 C/cm , keeping the dose for 50-kuV D irradiation the same at

0. 5 C/cm2, a reduction in blister density was observed for the simultaneous

5 2irradiation case (blister density ,6.5 t0 blisters/ cm ) as compared to

the two sequential and the single irr;adiation with He ions (blister density

for all three irradiations was ~1. 1 < 10 blisters/cm 2). While these

results are preliminary in nature, they have uncovered the existence of

important interactive effects. Reports on parts of these studies have

appeared in the proceedings of the Interri;itional Conference on Low Energy

Ion Bears, Salfo rd, V ngland, September, 1977 (Institute of Physics,

London, 1978), Inst. Phys. Conf. Se r. No. 31, p. 305.

d. Surface Structure After High Dose Helium Ion Irradiation of Materials

M. Kaminsky and S. K. D.as

In some recent studies of 100-keV helium-implanted Nb,2

the disappearance of blisters was reported for the high dose of 20 C/cm

The authors observed a sponge-like surface structure which they con-

sidered to be an equilibrium surface structure, and they concluded that

blistering is a transient phenomenon. However, since sponge-like sur-

faces have been observed at much lower doses (e. g., 1 C/cm2), but for

high target temperatures (homologous temperature X0. 5), it appeared

possible that the results reported in Ref. 1 were not typical for high-dose

implantations, but for high target temperatures (c. g., target heating by

deposited beam power 30-100 W/cm2). To clarify this point we have

started systematic studies of the surface structure of a number of

materials of interest to fusion reactor applications (e. g., as materials for

first wall, liners, beam dumps or limiters) for irradiation with either

100- or 250-keV 4He+ ion irradiation for doses up to 1.2 X 1020 ions/cm2

For such high-dose irradiations, no "equilibrium surface condition" was

195

VIII. Cd

TY PE 3 16 ST. S TEEL4500 C

-- 'V

J VO00i

," ' PVqWV,

V, 1 Lt-" .

Fig. 48. (a) Scanning electronmicrograph of Type 316 stainlesssteel irradiated at ~450 0 C with100-keV 4 He+ ions to a totaldose of 20.0 C/cm 2 . (b) Anenlarged view of one of the holescreated due to multiple exfolia-tion. (c) An even higher mag-nification micrograph of anotherhole. Notice that the thickness-es of the exfoliated layersmarked by arrows 1-15 arenearly the same.

observed. For example, for Nb

irradiated at 4500 C with 100-keV

4 + for the same dose of 1. 2 X 1020

2ions/cm , exfoliation of many

blister skins (in some areas more

than 3 skin layers of -"0.3 m

thickness) was observed.

Figure 48 shows at

th ree magnifications the seriously

xloliated surfaces of 316 stainless

steel. An "equilibrium surface

structure" has not been formed.

Instead, in many areas ("deep holes,"

0.1 to 1.0% of irradiated area) 15

skins have been lost, each of

~0. 55 0. 05 4m skin thickness

[Fig. 48(c)], and in addition, two

skin layers appear to have been lost

compl tely.

Under the assumption

that two skins have been lost, and by

adding the loss of skins in the area

of the deep holes, a lower limit for

the surface erosion yield has been

estimated as ".0. 1 atoms/ion. In

turn, an estimate of the upper limit

nor tn.! erosion yield (assuming the

complete loss of 15 skins), gives a

value of 0.7 atoms/ion. It should

be noted that even the lower limit

value for the erosion yield is one

196

1

VIII. Cd, e

order of magnitude larger than thL phvsiaI sltrte ring Vield valtac calcu-

lated.

The results rpuOrtcd here d i i,(t zp, r' thie (laivm made

for 100-keV 4i+ implantation of sulids to hijgh dOSts )f 20 C(/'t 2 that

blistering will be a transient phenomenoni, mnd thl. an <uiibrirm surface

structure ("sponge-lik(e'') will be term I'. (st .s- r a < ontinuous

exfoliation process of the irradiated sur, es.> o or th r materials

such as Al, V, Be, and l) a re in progress . H )rts U: Vt s ,f these

studies will appear in Proceedings of 7th I:itr nl; iji; I (onf rice on

Atomic Collisions in Solids, Mosco\, pt i, . n wi Jemrnal of

Nuclear r Materi;ls.

e. SurfacgeDa r c, (,f Mater i ls 1ur ti r

Irradiation

'v1. Kaminsky, S. K. Das, and 1'. l)is ',

udies have been c(monti td pi ) r (pi t t fry>m the

Princ ton Plasma -hysics L.a)bortorv (PPP I) to <I t(rnine W h surface

damage of rnolybd( nunl and a moybdcrnw H . ( >2), mndidjtc materials

for the neutral beam injector beam dumnp fu r I rim k1on's luk1ak FusionTest R- actor (TFTR), under the iiripat 1Of int e I) ionls uinderi condition

to be expected during the opt ration of T 1Tl. Spw, ifi( .h1 , tie s surface

damage of polycrystalline molybdenum and 1 7ii nd(Ir 10-, 60-, and

120-keV 1) impact ha s been inve tiga t( - ftr t ;t, tt n in bcth pul se d

and continuous mode for total doses va ry ing fru0m 1.7 1()17 to 2. 2 Y 1019

ions, cm and for target tempra-itures va rying f ronm :innbient tetme ratu re

to 400 C. Analysis by scanning electron nic-ro s (op' t the M( s a mpl's

held at ambient temperatures during D irradiations in both pulsed and

continuous modes revealed surface dama gL- due to blistering for the -40-keV

and 60-keV irradiations for doses ranging front 8.7 1017 to 8. t x 1018

ions/cm2 but no detectable damage for th#- 120-keV I) i irradiations for

dfI 19 2doses ranging from 4. 3 X iU to 2. 2 X< 10 ions/cm . This observed

1 97

VIII. Ce -g

difference in the blistering behavior is attributed to the differences in the

ambient target temperature for the 120-keV irradiation and both the 40-

and 60-keV irradiations. For irradiations at temperatures above 300 0 C,

no blisters could be detected for any of the three energies. For similar

irradiation conditions, TZM alloy showed a reduction in blistering as

compared to molybdenum. Reports on parts of these studies appeared

in J. Vac. Science and Technology 15, 710 (1978).

f. Sputtering Yields for Mo Under D Irradiation at Energies Characteristic

for Neutral Beam Injectors (TFTR)

M. Kai insky and P. Dusza

Studies are in progress to determine th. total sputte ring

yi'ld of polyc rystalline Mo under bombardment by D ions with en rgiies

o' 10 keV, 40 keV, 60 keV, 80 keV, and 120 keV. There exists a complete

lack of data for this energy range, yet the data are needed by the TFTR

designers to det'-mine the Mo release from the neutral beam injector beam

dumps (made out of Mo) in order to estimate the plasma impurity buildup

by the released Mo. The experiments are conducted at background pressures

o' 2-4 / 10 tortr, and for the detection of the collected sputter deposits,

R1i therford backscattering and sputter profiling with the scanning Auger

spectrometer are being used. The target surfaces were characterized

before and after irradiation with scanning electron microscopy in c on-

junction with an x-ray spectrometer and with scanning Auger spectroscopy.

The measurements will be extended luring 1978 to energies of 1 keV, and

the results will be cormpa red with existing sputtering theories.

g. Joint ANL-Kurchatov Institute Experiments on Radiation Blistering

M. Kaminsky, S. K. Das, M. Guseva, V. Gusev,* and Y. Martynenko"

In the continuation of the joint experiments between the

Kurchatov Institute and ANL, surface damage and erosion of Nb caused

Kurchatov Institute, Moscow, USSR.

198

VIII. Cg, h

by helium ions having an energy spectrum typical for T -20 are being

studied for doses higher than those used previously. The energy distribu-

tion arid flux of helium ions expected to strike the first wall in T-20 was

theoretically estimated assuming ion temperature of 7-20 keV end plasma

edge temperature of 1 keV. Using these estinaatts, niobium targets were

sequentially irradiated with He ions having c-nergies (in keV) of 0. 5 1,

2, 3. 5, 5, 8, 13, 20, 45, 65, 90, 150, 200, 300, 500, 1000, 1500, 2500,

3000, and 3500. The irradiation was sta rted at 3. 5 MeV and continued

up to 0. 5 keV. The results are being evaluated.

h. Joint PPPL-ANL Experiments on amclu Ir rdiated in PLT

M. Kaminsky, S. K. Das, and S. K. Lar

In a joint experiment with P in tin Pl a s ma Physics

Laboratory ( PPP L), su rfa ce damage of ta r get s and deposits cii collectors

expos. J to pila smi a discharges in Princeton's Large Torus (PLT) have

been investigated.

Two stainless steel targets exposed to plasma discharges

in PLT were supplied by Dr. S. Cohen, PPPL. One of the targets was

a stainless steel cap for a bolt holding the limiter aind was exposed to

plasma discharges (predominantly hydrogen) during the period between

20 December 1975 and 30 March 1976. The other target was a lype 305

stainless steel exposed to H12, D2, He, H(+ Ar, I1 + Ar plasma discharges

during the period between 30 June 1976 and 1 December 1976. This

target was mounted on a flange so that the target surface was recessed by

,10 cm from the outer limiter tip and ~4 cm from the vacuum wall.

The irradiated area of the stainless steel cap showed evidence of melting

and cracking in several places. It appeal rs possible that melting could have

been caused by runaway electrons and the cracks could have formed by

severe thermal stress gradients caused by localized melting. In addition,

some titanium deposits were identified on the surface by energy dispersive

x-ray analysis. The titanium has very likely been released from the

1 99

VIII. Ch

titanium bolts (which had lost their protective stainless steel cap) holding

the limiter in place. Examination of the Type 305 stainless steel target

did not show any detectable surface damage. The irradiated and unirradiated

areas (a portion of the target was marked off) of the surface were almost

identical as far as surface topography is concerned. Since the target

was recessed -".10 cm from the limiter tip and ~4 cm from the vacuum

wall, it is possible that the target surface had a relatively small exposure

to particle fluxes from the plasma discharge. Here were approximately

104 discharges of ~i1 second duration; with an estimated flux of 01052

particles/cm -s to the walls, the maximum exposure of the wall would be

~1019 particles/cm 2; the particles have a mean energy of .200 eV. Oi

this exposure to the wall surface, the recessed stainless steel target

may have received only a small fraction.

A Si collector received from P1PPL had been expos-d to

PLT irradiations for a six-month period (July to December 1976).

Typical Auger spectra of the Si-collector area which had been exposed to

the plasma radiations show C, O, Fe and W contamination, which is

actually so severe that it obscures greatly the Si peaks typical for th(

collector material. The Auger spectrum of the same coll ector . rea,

after it had been "sputter cleaned" by 2-keV a rgon ions for 260 minutes,

shows a reduction of the C, O, Fe and W deposits, and that the Si peaks

have become the dominant peaks. An Auger spectrum of a Si-collector

area which had been shielded from the plasma exposure by steel strips,

shows C and O contamination but not Fe and W contamination. Sputte r

profiles of the C, O, Fe and W contaminants and of Si substrate surface

layers show significant variations in the oxygen concentration during the

260-minute sputtering period, while the C, Fe and W concentrations show,

in general, a decrease in concentration as the sputtering time increases.

This result suggests that at different times during the six-month exposures

to the PLT plasma, different amounts of oxygen have been adsorbed.

From the areas under the curves, a crude estimate of the Fe and W

200

VIII. Ch 201

contanination c one nt r;.tion (bascd on Nb on Si calibr;ition experimentss)

his been rnade , t nd in q tui vd lnt of -%-2() mounol-iycrs of i ron and 12

rnonoV rs of tungst en has been doternyu nod. It should be pointed out

thait Dr. Cohen oscrverl for other I' IT i r radiation periods (some of

them six rn ths in length) I' e amd W (lepusit, on Si which wore sometimes

more than ten times as thick as those reported here. )ifferonces in the

'I.'! ope rating conditi ar s may h L r(esponsibh- for the differences observed.

VIII. 1)

D. PJIOTOIONIZATION-PH-iOTOELICTRON RESIEARCIH

Current experiments are aimed at understanding the basic

pro (esses determining the interaction of light with molecules, and utilizing

this information to infer the electronic structures of molec ules and molecular

ions. Th unimolec ul a r decay of (xcited molecular ions and the :imo secular

in sonc ca s(s, tcrmolecula r) reactions <of these ions are also being

investigated.

New activities being pl;inned include the following.

(1) The study of m e (ta l ;!torn s by photoioriii tion at photo-

electron spectroscopy. Atoms of only about 12 of the 100 or so clerrents

have thus fLir been investigated by photoionization. This is mainly bec. causeof technical difficulties with the high ternpe ratiures needed for sample

vaporization. We propose to 'mndertake the study of many atois using a new

oven system that is ned ring completion.

(2) The reactions of species in selected d states. Knowledge

of such rea tonss is needed for modeling of m1;any systems, c. g., planetary

atmospheres. In ca rlier work, it was found that in some < cases auto-

ionization populates selected ionic states whose properties could thus be

investigated in a sn;ull class of systems. We propose a more general

attack, in which state selection would be achieved by photocle troll-photoioncoincidence techniques. We plan to extend such measurements to nigher-

energy states th;un ha vc heretofore been studied, using line sour es 1ut to40.8 cV. A different type of bimolecular study wolIId involve the rcac tion

of selected neutral Rydberg states with various collision partners. 'Ihis

inte reaction normally leads to two competing channels, chemi-ionization and

colli sonal iorniza tion.

(3) An aIternative method for gaining insight into Jh( stabilityof molecula r-ion sta tcs is to irradiate molecular ions with la setr li ght ofvariable wa vclength, and thence to explore possible reaction products.

Our experimental. studies utilize four pieces of appa ratu s-

two photoionization mass spectronmetcrs and two photoelectron energyanalyzcrs-each with special features.

202

VIII. D ia 203

1. RESEARCH USING THE ONE -NI ITER PIHOTOIONIZATION APPARATUS

J. Berkowitz, J. H1. 1). F.and, and C. H. Batson

a. Photodissociative Ionization of Methanol

The photodissociative ionization of C1 OH1 has becn investi-3

gated from threshold to 20 eV. Th ions C Il 2 0lH (CI3),

CHJJOH+ (C;12+), 1C0+ ((01-+), CII3 , nd (112 w\\re examined. The

ambiguity in some of the decompositions (shown in 'renthses) was

resolved by using samples

16.0-(eV photon cnc rgy the

of CI)3OH Iand CH3C 1.O

structure CII 01+ is at

F(r example, at

least 13 times as

(0)

Mc T1:.'v

(b) I F>

*1

C,

4,>"J!-

'j)

\'QNA! FNEPGY (er

Fig. 49.V M32;

(a) Experimental breakdown diagram ofO M31; O M30; A M15; X M29; + M

mietha nbi14. (b) Calcu-

lated breakdown diagram of methanol.

0 L 1 .L~

's-

I , I

I

,( r

VIII. DIa,b

abundant as CH3O , and HCO 10 times more abundant than COH The

CD3 from CD3OH was 63 times as abundant as CD2H , which was the

level of isotopic purity of the sample. These results have obvious implica-

tion for the relative stability of the alternative structures. In addition,

the photoion yield curve of each of the ions was differentiated and summed,

to construct a normalized derivative curve, or breakdown diagram (see

Fig. 49). Among other features, this diagram revealed that CTI 3 , a

2major fragment, is grossly underestimated (by X10 ) by the quasi-equili-

brium theory, and very likely results from a direct dissociative process.

b. Fragmentation of Pyridine Ions and Heat of Formation of C H +4- 4-

Photoionization mass spectrometry of pyridine was under-

taken to complement previous photoelectron-phctjion coincidence studies,

and to pin down the heat of formation of the C IH fragment ion. A detailed4 4

analysis of the experimental rate constants and branching ratios in the

primary decay of pyridine cations to C H + HCN was made using the4 4

statistical theory of mass spectra. The data are well fitted by this theory

provided the transition state is made very tight, and the usual assumption of

complete energy partitioning prior to dissociation is upheld (see Fig. 50).

1I T

E) f XRE MELOOSE

CfMpL f X

1 1

-

/

0

IGHT C

.

j .(OMI E

10 .A 1 .. _.1 1 a3.2 3.4 3.6 3.83 4U 4 2 44 4.6

INTERNAL ENERGY1 OF C,3t1N'(V

Fig. 50. Experimental rate constants inpyridine-ion decay as functions of the internalenergy. The empty error boxes are fromcoincidence time-of-flight peak shapes, and

the stippled boxes from the metastable-ionintensity-peak positions in the breakdowndiagrams.

204

VIII. DIb;2a

The fitting sets limits of 277 to 282 kcal/mole for the heat of formation of

C4H4 , confirming a probably cyclic structure of this ion. This work is

now ready for publication. We expect to be able to use the theoretical

and data -handling methods developed for this problem in future studies of

ion fragmentation, particularly to cha racterize cases where the complete

energy partitioning, envisioned by the quasi --equilibriuni theory, does

not occur.

2. R FSFA1: CU USING 1111HETIR F1 -M T FR P1OTlOIONIZATIONAPPARATUS

J. Berkowitz, J. H1. 1). Eland, C. I1. Batson, and K. Radler

a. Franck -Condon Fa actors in the Photoionization of H1

In the process 112 (v" -0) + hv 4 112 (v' =0, 1, 2, ) + e,

the relati\ e probability of forming H in its various vibrational levels is

governed by Franck-Condon factors, but also by a small variation in

transition moment due to the different internuclear distances of H 2

(v' = n), and to the differing electron energies, when hvy is constant.

Theory and experiment are in reasonable agreement when hv = 21.2 eV.

However, at 1w "16.8 eV, calculations by Itikawa had resulted in similar

relative vibrational intensities as at 21.2 eV, whereas some experimental

results indicated a quite different vibrational distribution. It had been

stated that one of the two neon lines at X16.8 eV coincided with an auto-

ionization resonance in I-I2, which could distort the vibrational distribution.

We have examined the photoionization spectrum of H2 in this region.

Although there are weak autoionization features throughout the region,

they project above the direct ionization continuum only by about 10'.

No specific autoionization features fall directly at the positions of the neon

lines. Iience, the autoionization explanation for the discrepancy between

theory and experiment is most likely invalid. Our own photoelectron

205

VIII. D2a -c

spectroscopic studies are not in agreement with those which initially

focussed attention on such a discrepancy.

b. Comparison of Photoabsorption and Photoionization of N at HighRest1ution

Between the ionization threshold of N2 (~796 A) and ~730 A,

photoionization spectra are dominated by strong autoionization features.

The structure is described by a process in which light is absorbed to a

quasi-discrete state above the ionization threshold, followed by an

intramolecular interaction resulting in electron ejection. A competitive

intramolecular interaction can cause dissociation of the molecule into two

neutral entities. The photoabsorption process measures the sum of the

decomposition processes, whereas photoionization measures only the

autoionization component. A comparison of the two results can provide

information about the branching ratio, i. e. , the relative rates of the two

decomposition processes. Such a compa rison was made by us earlier with

poorer (0. 12 A) resolution; we have now performed a photoionization

measurement at 0.035 A resolution, and are in the process of comparing

our results with recent photoabsorption measurements performed wit.1

comparable resolution at the JORIS storage ring in Hamburg. There are

some notable differences, pa rticularly in the near threshold region, but

systematics and specificity to particular Rydberg states have not yet been

established.

c. Photoionization of Argon at I ugh Resolution: Collisional ProcessesLeading to Formation of Ar +

2--

We have obtained the photoionization spectrum of Ar from

threshold to beyond the P i/2 continuum, at a resolution of 0.02 A

(FWHM). At this resolution, the sharp s-like feature is broader than the

instrumental resolution, and enables us to estimate a natural width for the

first s-type autoionization of -0.4 meV. The broad d-type resonances

206

VIII. D2c

-9

rj~4 1 .

Fig. 5 . Expanded section of the collisionally induced Ar+ andAr 2 wavelength-dependent spectra. The Ar+ was obtained

with 0. 02-A photon resolution, the Ar 2 + with 0. 07-A photonresolution. Also indicated on this figure are the positions of

various Rydberg members and a crude photoabsorption curve

obtained in the present experiments.

have been fitted by the 1arametric form suggested by Fano. For the first

two (9d' and lOd') resonances, we obtain width parai f-cers I of 0. 00648

and 0.00412 eV, respectively, while the corresponding q parameters a re

1.69 and 1. 90. The significance of these widths is discussed in the

section VIII. D2d below, on neon.

At higher pressures (ca. 5 X 10-3 torr) collisional processes

are observed, leading to the formation of Ar2 Below threshold, the

process

Ar + Ar -+ Ar + e2

(sometimes referred to as a Mohler-Franck or a Hornbeck-Molnar process)

is the mechanism. Peaks occur in the Ar2+ spectrum at energies corres-

ponding to absorption of light by Ar to various P states. This latter

process is competitive with a collisional ionization

Ar + Ar 4 Ar + Ar + e.

In the region just below threshold, the collisional ionization mechanism is

dominant, but at longer wavelengths, the process forming Ar2+ takes

precedence (see Fig. 51). We have analyzed the observations in terms of

2 07

r

"' I

1

VIII. D2c, d

oscillator strengths, and collisional cross sections based on recently

calculated potential curves for Ar and Ar. These processes and their22

respective rate constants need to be known for a proper modelling of the

phenomenal that occur in high-energy rare-gas excimer lasers. A paper

has been completed on this wo-k and will soon be submitted for publication.

d. Photoionization Mass Spectrometry of Neon Using Synchrotron Radiation

Some time ago we obtained the photoionization spectrum of

2neon from threshold to beyond the onset of the P cc~ntinuum. This

1/2experiment could not be performed with our laboratory light source,

which has no output in this region, and hence was investigated using

synchrotron radiation from the electron storage ring at Stoughton,

Wisconsin. We have now analyzed these data and compared the auto-

ionizat' >n structure with corresp )nding structure in Ar, Kr, and Xe.

In all .1 cases, there are two types of resonances, resulting

from excitation to s-like or d-like Rydberg states. The autoionization

widths of the s-like states are a factor 10-20 narrower than the d-like

states, a nd only a few resonances in Ar, Kr, and Xe are sufficiently

broad to be observable with our resolution. The d-like resonances are

broad enough to permit analysis in terms of Fano's parametric fit. For a

given series in a pa rticular atom, the width F varies inversely as (1 ) ,

where n is the effective principal quantum number of the Rydberg -lectron.3

Hence, the product (n ) 1' is a measure of configuration interaction strength

in the autoionivation process. Surprisingly, this product does not behave

monotonically in the noble gas sequence. It is about 4 for Xe, 2.4 for Kr,

again about 4 for Ar and <2 for Ne. A theoretical analysis is currently

under way to try to rationalize this behavior.

208

VIII. D2e

e. Photoionization Studies of Molecular Autoionizing Line Profiles in

COS and N 2 0

In an earlier high-resolution photoionization study of N2C

we discovered that certain molecular autoionizing resonances have

different profiles when observed in different ion channels, as N2 0, NO+,

or O , for instance (see Fig. 52). The profiles reflect interactions of the

resonant states with different ionization continua, corresponding to

different states of the molecular ion formed in the autoionization step.

On general theoretical grounds it seems that there should be relationships

between the line shapes, partial strengths, widths, ewrgies (rluantun

defects) and symmetries of the states

involved. We have begun to seek such 3dn

relationships both theoretically and

experimentally. Suitably isolated

resonances in the photoion-yield curves RESO UTION

of COS+ nd S from COS, and in the

N20-ie yield curves are being

analyzed using extensions of the Fano 4

theory. The main conclusions to date

are that all m.,nifestations of a single -

resonance in different channels can be -. /

represented using the same E (energy) -

and I' (width) values and can be fitted to

the single-channel-profile formula.

The last conclusion contradicts current 0+

theory, from which a more complex

666 667 668 669 670peak-profile formula (not reducible WAVELENGTH (A)

to the simpler form) has been derived

for partial cross sections. Tests of Fig. 52. Two N 2 0 resonances asthey appear in four partial

the theoretical version are in progress. photoionization cross-section

curves, showing differences in

shape and peak position.

209

VIII. D2f

f. Photojonization Mass Spectrometry of CS and C2 N2

The fragment ions S and CS+ from CS 2 , and the C 2

fragment from C 2 N 2 (cyanogen) each appears in photodissociative ionization

at an energy where no state is found in the photoelectron spectrum.

Direct ionization is therefore unlikely to explain the formation of these

fragments near threshold, so they may be formed by a hitherto

unrecognized mechanism. We have examined the photoion yield curves

for these ions and the corresponding parent molecular ions at high

resolution to try to determine the formation mechanism, and also to test

whether or not their r m measured onsets match the thermochemical thresholds.

It is normally assumed that fragment-photoion onsets are equal to the

thermochemical thresholds, and this assumption is used widely in the

determination of bond energies by photoionization. It is not understood,

however, how they can be equal when they fall in empty photoelectron

regions, and they are definitely not equal in at least one such case

(NO+ from N 2 O). The measurements show that all three of the present

fragment ions do appea r at energies very close to the thermochemical

thresholds, but the shapes of the ion yield curves are such that the usual

extrapolation proc edure to determine precise appearance potential cannot

be applied. The (approximate) appearance potentials of CS+ and S+ from

CS2 are nevertheless sufficiently precise and consistent to decide between

alternative values of the dissociation energy of CS 2 , and to show that a

recent low value for the heat of formation of CS is in error. The mechanism

of formation of S from CS2 at threshold seems to be autoionization to

parts of the ionic hypersurface outside the Franck-Condon region, while

in the other two cases direct ionization near threshold to hitherto unknown

states of the molecular ions may be involved.

210

VIII. D3a, b

3. PHOTOELECTRON SPEC TROSCOPY RESEARCH

J. H. D. Eland, J. Berkowitz, C. H. Batson, and J. E. Sherman

a. Weak Bands in Photoelectron Spectra Excited by 1ie I and le II Light

From our work using photoionization mass spectrometry,

it has become clear that a hitherto unobserved state of N20 exists near

15 eV, a similar state of CS2 near 19 eV, and possibly a state of C2 N +

near 17 eV. In addition, there are doubts about the existence, strength

and location of several high-energy states found by others in photoelectron

spectra taken with 1-ie II excitation. We have begun a direct investigation

of these points using two photoelectron spectrometers: first, a cylirdrical

mirror analyzer which yields accurate relative band intensity, and

secondly a hemispherical analyzer which gives a very good signal-to-noise

ratio, needed in the initial s-arch for weak bands. Partial cross sections

have been obtained for excitation to high-lying states of O, C , N2 0

and NH 3 , using filtered He II light, and possible n( w states have been

discovered in N 0 and CS . This work is continuing.

b. Photoelectr(n Spectra of Tetrachlorides of Metals in Group IVa

As part of our program on the spectra of high-temperature

species, we have measured the photoelectron spectra of TiCl, ZrCl4 and

HfCl4 and propose to study ThC14 soon. While the electronic structure of

TiCl4 is relatively well understood, those of the heavier tetrahalides are

unknown, in particular the f-shell structure in the hafnium and thorium

compounds. 'Ve intend to study the f-shell photoelectron spectra using

He II excitation, to compare with theoretical calculations of the molecular

orbital structure.

211

VIII. E

E. HIGH-RESOLUTION SPECTROSCOPY OF ATOMIC BEAMS WITH

TUNABLE LASERS AND RADIOFREQUENCY TECHNIQUES

W. J. Childs, L. S. Goodman, and O. Poulsen

The classic Rabi atomic-beam magnetic -resonance technique

for studying details of atomic structure has in recent years been supple-

mented by a variety of laser techniques. In particular, the Doppler-free

fluorescence spectra obtained by exciting well-collimated atomic beam

with a tunable, monochromatic dye laser have made possible the detailed

study of much higher-lying levels.

The initiation of such studies on a barn of lanthanum was

mentioned in the last Annual Review. Since then, precise values of hyper -

fine structure (hfs) constants of many excited, odd-parity levels have been

measured. A concurrent theoretical program has obtained eigenvectors

for the states of interest by simultaneous iterative diagonalization of the

six lowest odd-parity configurations. Evaluation of the expectation values

of the hFs constants using these eigenvectors then provided linear

expressions for the measured values. Least-squares fitting of these

expressions to the experimental valiies determined some of the hfs radial

integrals, but the high quality of the experimental data now available will

require much more precise eigenvectors than those so far developed.

Several fluorescence spectra were obtained from a beam of

uranium, and the .20 MHz linewidths observed for individual hfs components

are about 30 times sharper than the best previous work. This program

will be continued.

The rf-laser double-resonance technique, developed in

1975 at the Universities of Western Ontario and Bonn, has recently been

applied to an atomic beam of samarium. In this technique, which is

resonant in both the optical (laser) and radio frequencies, a transition

between two hyperfine levels of a metastable state can be observed by

noting an increase in the laser excited fluorescence of the beam. One can,

212

Sm iA 5874.2

-F

-- ooolA

Smj4'C) '- 4-

44

I I' G

9000 8400 7800 7200

Sm 4 "

15'1HK-

i Y50

JI8

I44

Fig. 53. Fluorescence obtained from a collimated atomic beam of

samarium by scanning a monochromatic laser in the region of

5868.60 A. The hyperfine structure of the odd-A isotopes 147Smand 1 4 9 Sm, and the isotope shifts of all seven naturally occurringisotopes can be seen. The linewidth is about 4 MHz or 5 X 10-5 A.

The numbers above the lines give the F values of the initial (lower)

state and the final state.

with this double-resonance scheme, measure the hyperfine intervals in

the lower state with a precision 1000 times better than is feasible with the

usual laser techniques alone. A new, very compact apparatus was

constructed for this type of study early in 1978.

Figure 53 shows a laser scan through a single line in Sm.

The five components due to even-A Sm isotopes are labeled; the others

arise from hfs in the two odd-A isotopes. Although the figure shows

fluorescence resulting from absorption from a member of the 4f 6s2 7F

ground multiplet, strong fluorescence can also be produced from metastable

VIII. E 213

VIII. E

A E 8

APPLIED RF FREQUENCY ( M Hz)

8 x103

V

states populated by a discharge in the atomic beam. A plot of fluorescence

intensity vs applied rf frequency in a double-resonance experiment on such a

metastable state is shown in Fig. 54. The hyperfine interval is easily

determined to 0.4 kHz, while a determination of the same quantity to

0.4 MHz is difficult using laser fluorescence alone. The lower level

from which the absorption occurred is at 11,044 cm-1, and is populated

in the atomic beam entirely by the discharge. Such measurements have

been made on a number of levels in Sm.

ve=320.6717 (3) MHz

147S'Sm- f 6ds 9H 2

11,044.90 Cm

15 kHz

- -..*g

- ..

7

6

5

4

0

Hz

wiU

U

0

Lii

U)M0

Fig. 54. Rf-laser double resonance

in the metastable 4f6 5d6s 9 H 2state of samarium at 11044.90

cm- 1 . The intensity of the

observed fluorescence is plotted

as a function of the radio frequency

applied. The precision is about

1000 times better than that

achievable by customary laser

fluorescence techniques alone.

l I 1 l I

214

3

VIII. Fa

F. MOSSBAUER EFFECT RESEARCH

In the two decades since its discovery, the Mossbauer effect

has become a mature field with many applications. The program reported

here continues to have as its goal the exploration of new and potentially

important extensions of the discipline. The present thrust is threefold:

(1) experiment 3 with narrow resonances, (2) radiofrequency techniques and

coherence studies in Mossbauer spectroscopy, and (3) studies of specialized

solids.

The first category includes experiments with the ultranarrowresonance in 6 7 Zn and attempts to improve the width of the resonance line

in 18 1'a. No work with the Zn resonance is reported for this period, but

it remains an essential part of the future program. The tantalum resonance

has been the object of a considerable effort by G. Wortnann, a visiting

scientist from the Technical University of Munich.

The second category contains the continuation of work on

ultrasound production in low temperature copper and new experiments

on y-ray quantum beats. The latter are potentially important in connection

with category (1) for the detection of very small energy shifts due to

relativistic effects.

In the third category, this report discusses continuing experi-

ments on the intercalation compounds of xenon fluorides in graphite,including some ancillary measurements on electrical conductivity. Prep-

arations for experiments bearing on a connection between Mossbauer

spectroscopy and superconductivity are also described.

Outside of the three categories above, but still representing

a considerable labor during the past year was the organization of a Workshopon New Directions in Mossbauer Spectroscopy held at Argonne in June 1977,and the subsequent editing of a proceedings that va: published as a volumein the American Institute of Physics Conference Proceedings series.

a. Generation of Delayed Ultrasound in Low-Temperature Copper

G. J. Perlow, W. Potzel, and W. Koch

The Mossbauer effect is a very sensitive detector for high-

frequency acoustic signals. An emitter in motion at 10 MHz gives a readily

Technical University of Munich, Munich, Germany.

215

216 VIII. Fa, b

discerni:.ile effect for particle amplitudes of 10 cm. We have used

this sensitivity to search for the production of ultrasound in a low-temperature

copper foil which is carrying a pulse of radiofrequency current. What

was found was that sizable ultrasound amplitudes are produced after the

pulse, typically 2 4s in length, is turned off. It reaches a peak about

100 s later. The foil is doped with 57Co and the acoustic motion is detected

by the frequency modulation of the 14. 4-keV Y ray of 57F_ produced in its

decay. A considerable variety of experiments has been done on the effect.

It appears to be associated with instabilities in the helium bath connected

with the transfer of heat from the foil. Analysis continues. A preliminary

report has been published. 1

G. J. Perlow, W. Potzel, and W. Koch, Journal de Physique 37,C6-427 (1976).

b. Intercalation of Xenon Fluorides into Graphite

* tL. E. Campbell, H. Selig, and G. J. Perlow

The intercalation comp ound of XeF6 in Grafoil, an oriented

graphite-sheet material, has been studied by Selig and others as a fluorinat-

ing agent. An NMR study of the fluorines indicated an anomaly in the

composition. The Mossbauer effect is a good tool for nondestructive

identification of xenon compounds and led to this project. The XeF 6

intercalant was studrea in Grafoil and in an oriented graphite host. In

neither is there any trace of XeF 6 , but rather a prominant XeF 4 component

with possibly some XeF 2 . A study of XeF intercalated into Grafoil

showed evidence for a strong admixture of XeF2. XeOF 4 appears to remain

unchanged upon intercalation. Experiments elsewhere have shown that

AsF5 intercalated into graphite produces an artificial-metallic electrical

conductor, with high conductivity in the graphite plane and very much lower

Hobart and William Smith Colleges, Geneva, New York.

tBell Laboratories and Hebrew University of Jerusalem, Israel.

VIII. Fb, c

conductivity in the- perptndicula r direction. Mea suremcnt s were made on

the xenon-fluoride samples on hand to see if enhanced planar conductivity

could be observed. This was done by an eddy current method similar to

the one employed previously in the work on AsF5. There were no dramatic

improvements in electric I properties observed. This project is sub-

stantially complctcd and t paper - is in prpa ration.

c. ( onfe rence on New Directions in Mossbauc r Spectroscopy

G. J. Perlo\w and E. P. ..,nakin

P egular international meetings on the applications of Moss -

baucr spectroscopy are held in the western countries every other year.

They emphla siz (1) propcrti(s of specialized solids, (2) chemistry, and

(3) biology. It was felt a dvisable to convene a conference in which these

subjects w re primarily excluded. In keeping with the desire for a less

formal arrangement, it was titled 'Workshop on New Di rectiol- in Moss -

b;tuer Spectroscopy. " Th( conference took place on June 10 and 11, 1977.

The topics were:

(1) New and neglected techniques

(a) Synchrotron radiation as a M ossbauer source

(b) Focussing and guiding of y rays

(c) Rayleigh scattering (recoilless)

(d) Ultralow temperature

(2) Coherence phenomena

(3) Isotopes of special interest

(4) "Sensitive expe riments" (relativity, etc. )

(5) Nuclear physics

(a) electromagnetic moments and moment distributions

(b) Symmetries from Mossbauer experiments

(c) Experiments in accelerator beams

(6) Other experiments, ideas, or theories that fit within the frame-

work of the Workshop title.

217

VIII. Fc,d

Attendance:

(1) Somewhat selective

(2) 62 registered, from 12 countries (plus auditors from the local

pnysies community)

A conference proceedings was published as: Workshop on

New Directions in Mossbauer Spectroscopy (Argonne 1977), edited by

G. J. Perlow,' (American Institute of Physics, N. Y. , 1977). It contains

26 papers, including a transcript of a panel discussion on uses of

synchrotron radiation.

d. y-Ray Quantum Beats1

Gilbert J. Perlow

This may be considered an experiment in y-ray quantum

optics. It is possible to do it with the recoil-free Mossbauer radiation,

because (a) the resolution of the spectroscopy is adequate to observe

the natural line width, (b) the emission lines have nearly the natural line

width, and (c) the lifetime of the nuclear states involved falls within the

region that can be measured with electronic techniques.

The 14. 4-keV radiation from the transition of the first-

577excited level to the ground state in 57Fe is emitted in the -y-ray decay

cascade that follows electron capture in 270 d 57Co. If the latter is doped

into any of a variety of solid host materials, a large fraction of the emissions

is recoil-free and displays the Mossbauer effect. In these experiments a

source of 5 7 Co, an impurity in i thin copper foil, was cemented to a thin

quartz piezo-crystal which was caused to vibrate at a frequency of 9.95

MHz. If this radiation is allowed to fall upon a scintillation counter and the

statistics of arrival times of the radiation recorded, one finds nothing but

a random time structure. The energy spectrum of the radiatior (measured

by the usual Mossbauer technique of using a resonant absorber and scanning

tGilbert J. Perlow, Phys. Rev. Lett. 40, 896 (1978).

218

VIII. Fd

the radiation in a transmission . ..

experiment) shows not the single 0 a NORMAL

line of an unvibrated 5 7 Co-Cu SPECTRUM20

source [Fig. 55(a)], but a (well-30.-

known) multiplet due to frequency o0--'; -

nodulation. It contains an z 2 - b) 9 (OA9 f SOJRW'E VIBRATED

unshifted carrier and sidebands C 4 t 995MHZ and,~ vl ms

Fig. 55(b)]. The latter are m 6

separated from the central R

unlshifted carrier by multiples of . /Y,

the modulation frequency, 9. 95 ICENTFR LINEu f i REMOVED FROM b)

Mz. If now this multiplet WITH STATIONARY IFe -He ABSORBER

emission from the vibrated source 6L 15 -4 1 -2 I I I 2 3 4 5

is passed through a resonant VELOCITY (mm/sec)

medium (i . e. , one containing57 Fig. 55. Velocity spectra: (a) unmod-

Fie in some solid form), what ula -1 (b) frequency modulated at

is transmitted contains a time 9.95 MHz; and (c) frequency modu-

lated and filtered.structure with respect to the

y ray that follows the 57Co decay.

If the medium only absorbs at the carrier energy [Fig. 55(c)] , one finds

only the second harmonic, i. e. , 18.9 MHz and some higher even harmonics

in the counting rate (Fig. 56). The odd harmonics are suppressed.

A simple mathematical model gives insight into the origin

of the phenomenon. It appears as interference between the frequency-

modulated photon and the spectral hole produced by its pa rtial absorption.

All the observed time dependence is, in fact, due to interference between

the different frequency components of the photon wave function, and it is

for this reason that the term quantum beats applies. The interference

exactly cancels when al components are present.

If the absorber resonance is shifted slightly from the carrier

energy, the funcianental and the odd harmonics appear. The ratio Di /D

219

VIII. Fd

.12- CRYSTAL FREQUENCY 9.95MHz at IOV of the fundamental to the secondF-

- harmonic turns out to be very0.08

Z II sensitive to this shift and variesZ 0.04 t I } I

linearly with it. A possibleo-

z j application of the quantum beats

o -0.04 is therefore to the measurement

-0.08 . of small shifts, such as those

-L -1 -- L -_--_ -0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 caused by relativistic effects.

TIME (psec)The quirtum b, ;ts

Fig. 56. Time spectrum with the are directly related in phase to

radiation of Fig. 55(c).the mean phase of the motion- of

the source. One ma y set a time

*. f"- gate over some interval of the

- -. --. -" beaits and accept data pulses only

- during the gate interval. One may

then take the usual Mssbauer

velocity spectrum. Inth resting

55 4 4 and strange looking spec;.ra result

from such a mixture of the nime

Fig. 57. Velocity spectrum with;end frequency dloma~ins, whether

the cIoinditions of Fig. 55(c) butgated during a short portion of one employs the stationary ibsorb-

the beat cycle.er or not. In the latter case,

there are no beats, but the cime

gating still operates. In Fig. 57 one sees suc'i a spectrum (with the

station ry Fe- Be absorber in place) gated over a portion of the beat cycle.

Without the restrictive gating, it would be exactly the spectrum of Fig. 55(c).

One now sees dispersion-like transmission curves with counting rates in

excess of the background at some velocities.

220

VIII. Fe

181(. Experiments with Narrow Resonances: Ta (6.2 keV)

G. H. Wortmann

181The 6.2-keV Mossbauer resonance of 'a is one of the

"narrow resonances" which has been most widely applied to the study

of hyperfine interactions in solids, and has demonstrated its high-resolution

power by the observation of very subtle effects (e. g. , the hydrogen diffusion

in Ta metal). The reasons for the great utility of the 1T1'a resonance are:

the large (and aence favorable) value of the nuclear radius change ,(r2

a nd the large magnetic-dipole and electric-qua drupole moments. All studies

with the 181TF resonance to date have been performed with experimental

linewidths which exceeded the natural linewidth W = 6.5 pjm /s by at least

a factor of 10. It is obvious that an improvt-mnent in the cxperim ental line -

width would considerably enlarge the scope of applications of this resen-

ince. It is, therefore, the goal of the present work on 181'Ta to investi-

gatc th( reasons of the line broadenings end to produce sources and

absorbi-rs with a better linewidth. Two kinds of experiments are performed.

(i) Investigation of a possible contribution of the electric-

hexadecapole interaction (1-1. 1). I.) to the experimental linewidths. 181a

belongs to the class of strongly deformed nuclei and a hexadecapole moment

of about -1 ' 10 cm has been found from measurements on muonic and

pionic atoms. Taking this value and recently calculated Sternheiiner anti-

shielding factors for hexadecapole moments, the 1-1. 1). I. can be estimated

to be about 10-4-10-5 times smaller than electric -quadrupole inte ra ctions

in comparable matrices. The H. D.I. energy would correspond to a splitting

of the resonance line by ~1-10 pm/s, which is an observable magnitude.

We are preparing an experiment where the source (single crystal of cubic

Ta or W) is exposed to a small magnetic field, which splits the resonance to

a magnetic -hyperfine pattern of 24 lines. The H. D. I. (which is present even

in cubic symmetry) should manifest itself in specific deviations of the line

positions (roughly proportional to the fourth power of the nuclear magnetic

quantum numbers). Besides the interest in observing such a small

221

VIII. Fe

interaction, experimental values for the H. D. I. would be very useful

to test calculations about hexadecapole shielding factors and to get infor-

mation about the crystal electric-field strength in d-transition metals.

The velocity spectrometer has been modified for this type

of experiment. High-purity Ta metal absorbers ( 2 -4- m thick) have

been prepared by high-temperature annealing in UHV. The experiments

will be performed after receipt of a specially prepared source from Munich.

(ii) Preparation of narrow-line sources and absorbers

from (nonmetallic) single crystals of KTaO3 and LiTaO 3. The best line

w idths for the Ta reson, nee ha vt been observed in metallic systems.

There are rca sons to think that -n nonmetallic compounds, e. g. , in the

tantalates MTaO3 (M = K, Na, Li), better experimental line widths should

be observable. For instance, N. M. R. a nd N. A. R. (nuclear acoustic

resonance) results show better line widths in (cubic) KTaO3 than in (cubic)

Ta metal. Furthermore, the natural Mossbauer line width has been ub-

served with the two other "narrow resonances," 6 7 Zn and 7 3 Ge, in

nonmetallic systems.

We are presently producing sources by diffusing carrier-

free 18 W activity in a single crystal of KTaO3. The carrier-free activity

was produced by a deuteron irradiation of Ta metal at the Argonne cyclotron

and was separated by an ion exchange chromatography. The first source

prepared in this way showed no Mossbauer effect (the resonance velocity

is known from absorber experiments with polycrystalline K'aO3 ).

The experience gathered in performing a quick and effective

chemical separation of 181W from the rather hot Ta targets is contained in

a paper, which will be published together with co-workers from Munich,

w here the work on source preparation from cdrrier-free X8l\V activity

was started.

222

VIII. Ff

f. Application of MNssbauer Spectroscopy to Superconductivity

C. Falco, G. J. Perlow, and G. H. Wortmann

Phonons with energies greater than the gap energy 2A in

a superconductor can be absorbed by quasiparticle excitation, and conversely

quasiparticles above the gap can de-excite with the production of phonons.

In the latter case these tend to produce monoenergetic phonons having the

gap energy. If a superconducting foil is insulated by a thin layer from a

resistance material, and a pulse of heat is produced in the latter by

electrical means, phonons traversing the superconductor ;i re absorbed by

the first process if their energies exceed 2- and transmitted if not. The

absorbed phonons are converted by the second process (in considerable

pa rt) to a monoenergetic spike at the gap energy. It is proposed to do

experiments with these, almost monoenergetic phonons using the Mc;ssbauer

effect. The rationale for such a program is the knowledge that when a new

technique is brought to bear on an older subject, there is invariably insight

gained that could not have been obtained ea rlier.

The first experiment ,s presently planned will use a

resistive film insulated from a superconducting film (probably Pb-Sn),

a second thin insulating layer, and then a Mossbauer source of 57Co in Cu.

Phonons generated in the resistive film by the heat from a small current

pulse pass into the superconductor, are converted to the spiked spectrum,

and generate high-frequency modulation of the y quanta emitted from the

source. These have increased transmission through an absorber of 57Fe

in Be. It is proposed first to investigate the dependence of the transmission

on the parameters available in the phonon production, for example, the gap

energy 2A.

Solid State Science Division, ANL.

223

VIII. Fg

g. Iodine in Starch*

S. L. Ruby, R. C. Teitelbaum, and T. Marks

A long-standing problem in chemistry has concerned iodine

in starch. Upon oxidation, a deep blue-purple color is created and the

material exhibits an increase in conductivity. The amylose molecules form

a helical tube-like structure, and the iodine atoms string out inside the tube.

This was earlier considered to be an example of a linear metal. The results

of Mossbauer experiments have suggested that the iodine strings have the

structure I3 (traditional x-ray methods for determining structures could

not be used in this case). We have now repeated this work more carefully.

The results, especially when confirmed by parallel work using Raman

spectroscopy, now indicate that I5 is the most plausible structure.

A paper has been published in J. Am. Chem. Soc. 100,

3215 (1978).

Northwestern University, Evanston, Illinois.

224

VIII. Ga

G. MONOCHROMATIC X-RAY BEAM PROJECT

The purpose of this work is to verify experimentally some

of the new phenomena associated with nuclear Bragg scattering of x rays,and then to use them to produce from synchrotron radiation highly directional

and monochromatic x-ray beams. The frequency spread is expected to be

six orders of magnitude sharper than any existing betm; despite this, the

intensity into precisely defined angles (10- steradians) should be 210 c/s

in the first experiments. Sach beams have a coherence length of some

10 meters, and should make it possible to extend into the x-ray region the

techniques which the laser has brought to visible light-namely, long-path-

length interferometry and holography.

Our results to date have been (a) detailed computations onenriched, perfect single crystals of Fe and FeTi and (b) the design, installa-tion and preliminary tuning of the experimental facilities at SPEAR. In the

next few months, we expect to determine experimentally using Fe crystals

that the reflected beam is delayed in time by about 30 nanosec onds, andthat its fractional line width is 10-11. We expect this to be the first

demonstration of temporal dispersion in Bragg scattering.

In preliminary work, the detected beam is still expected to

be heavily contaminated by prompt electronically scattered photons.

Different crystals, used in special scattering geometries, are required toexploit more of the differences between nuclear and electronic scattering

to suppress this contamination. Producing such special enriched single

crystals will be a major part of our future effort. Work is also needed on

an improved x-ray holographic recording medium. New intense synchrotron

beams are becoming available with developments at SPEAR, Cornell, and

BNL. Our plans call for research on both crystals and detection methods.

a. Calculations for Multiple-Crystal Nuclear Bragg Scattering

S. L. Ruby and P. A. Flinn

Some numerical calculations on Fe single crystals had been

made by J. P. Hannon (Rice University). For corroboration and because

we need to consider reflections from multiple crystals, independent calcu-

lations have been performed here. Our treatment was closer in form to

that used for anomalous x-ray scattering, but our results agreed nicely

with Hannon's. We have considered carefully the displaced parallel (622)

reflections from a pair of iron crystals, as well as the antiparallel orientation

225

VIII. Ga -d

of FeTi using the (542) planes. The second case is experimentally more

attractive, but the crystals for the first case are now available.

b. Design and Construction of Coherent X-Ray Facility

P. A. Flinn and S. L. Ruby

A flexible, two crystal spectrometer was designed and built.

It is of novel design and is presently being tuned. Beam time at SPEAR

is very limited; we have gained time through I April 1978 by building an

experimental facility for a temporarily unused beam. The controlling

computer has been installed and is now functioning well.

c. Symmetric Radiant State in Nuclear Bragg Scattering

S. L. Ruby

Careful use of conventional theory (first done by Trammell

and Hannon) indicates that the scattered light is delayed only by a fraction

of the nuclear lifetime. It is not obvious why this light is speeded up in

comparison with nonresonant nuclear fluorescence. Consideration of the

intermediate state in Bragg scattering allows one to see how the enhance-

ment of the radiative channel occurs. These considerations lead to the

prediction of a "one photon in-two photon out" coherent scattering process.

We hope to look for this type of process in the future. This intuitive, yet

semiquantitative, treatment has been published.

d. Coherent Nuclear Scattering of Synchrotron Radiation

G. T. Trammell, J. P. Hannon, S. L. Ruby, P. A. Flinn, R. L.

Mossbauer,' and F. Parak'

A short version of our calculations on this topic has been

published and a more complete version is now being prepared. It describes

all of the presently known ideas, including those pertaining to thin crystals.

University of Munich, Munich, Germany.

226

VIII. Ge 227

e. Temporal Effects of the Hyperfine interaction

J. P. Hannon, G. T. Trammell, and S. L. Ruby

With Bragg scattering of synchrotron light, the intermediate

symmetric state involves many nuclei, some of which ire in every hyper-

fine level. Thus the interfering scattering amplitudes can have several

discrete frequencies at once, and the scattered radiation will show 'beats.'

Under the conditions of our experiment. where the nuclei are all in a

strong magnetic field, the beats will appear in time as shown in Fig. 58.

The vertical scale there does not yet reflect all the experimental complica-

tions and so represents an optimistic view, but the positions of the peaks

are fully determined. This new phenomena-it is rather lik the Fourier

transform of the usual energy spectrum-is expected to be obse -ved in

the summer of 1978.

6

5

Fig. 58. Temporal decay of anuclear excitation created by

synchrotron radiation on the g 3

Bragg angle for 5 7 Fe in an 2

enriched iron crystal. Arather complex 'half-life' ! z

o 40 80 120 160 200 240 280TIME (nsec)

VIII. H

H. SCANNING SECONDARY -ION MICROPROBE

MICROSCOPIC LOCATION OF TRACER ISOTOPES

V. E. Krohn and G. R. Ringo

The aim of this project is to improve the present ion-micro-

probe analyzer very significantly in space resolution and mass resolution

to make it a more useful instrument, particularly in biology. The ion-

microprobe analyzer generally uses a beam of primary ions focused to a

point whose diameter determines the space resolution of the instrument

and is at present I to 2 m. The primary beam is scanned over the

specimen and a map of the distribution of an element or isotope of interest

in the specimen is built up by detection of the secondary ions produced

in the specimen and analyzed by a mass spectrometer of appropriate

resolution, usually around 300.

We believe this instrument could be very useful in biology

to map isotopes such as 14C 170, etc. used as tracers. However, for

full usefulness it will be necessary to identify all the interesting secondary

ions (by resolving the various mass doublets).

To achieve high space resolution it is necessary to stop

the beam down to a very small diameter to reduce the effect of lens

aberrations. This means a very bright ion source is needed to get practical

yields of secondary ions. We have developed such a sources which uses

field evaporation of ions from liquid metals. Our source uses gallium and6 -2 -1

gives about 10 A cm steradian at 21 kV. We have shown that the tip

diameter, taper and length of the needle in the present source are nearly

optimal.

Supported by the National Institutes of Health.

V. E. Krohn and G. R. Ringo, Int. J. Mass Spectry. Ion Phys. 22,307 (1976).

228

VIII.H

We have essentially completed the construction of a secondary

ion microprobe using this source and other new technology which we have

developed. 2, 3 The shortage of funds, however, is going to make it difficult

to demonstrate the full capabilities of this device and will prevent the

investigation of new techniques for using 14C as a tracer. However, it

14 - 14may be possible to show that N is such a rare ion that C can be

identified with relatively standard mass -spectroscopy techniques.

A high-temperature source has been built to allow tests of

metals such as lithium, tin and lead. Also, tests are in progress using

liquid metal films on tungsten wires to form field emission sites.

2V. F. Krohn and G. R. Ringo, J. Microscopy (Oxford) 110, 59 (1977).

3 V. E. Krohn and G. R. Ringo, Rev. Sci. instrum. 43, 1771 (1972).

2 29

Publications

PUBLICATIONS FROM 1 APRIL 1977 THROUGH 31 MARCH 1978

The papers listed here are those whose publication was

noted by the reporting unit of the Laboratory in the 1 -year period stated

above. The dates on the journals therefore often precede this period,and some dated within the period will be listed subsequently. The listof "journal articles and book chapters," which also includes letters and

notes, is classified by topic; the arrangement is approximately that

followed in the Table of Contents of this Annual Review. The "reports

at meetings" include abstracts, summaries, and full texts in volumes of

proceedings; they are listed chronologically.

A. BOOK

1. WORKSHOP ON NEW DIRECTIONS IN MOSSBAUER SPECTROSCOPY(ARGONNE 1977), Argonne, Illinois, 10-11 June 1977, AIP Conference

Proceedings No. 38edited by Gilbert J. Perlow

American Institute of Physics, Inc., New York, 1977

B. PUBLISHED JOURNAL ARTICLES AND BOOK CHAPTERS

16 + - 161. PION NON-ANALOG DOUBLE CHARGE EXCHANGE: O(Tr , ) Ne

R. J. Holt, B. Zeidman, D. J. Malbrough,* T. Marks,* B. M.Preedom,* M. P. Baker,t R. L. Burman,t M. D. Cooper,tR. H. Heffner,t D. M. Lee,t R. P. Redwine,t and J. E. Spencert

Phys. Lett. 69B, 55-57 (18 July 1977)

University of South Carolina, Columbia, South Carolina.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

231

Publications

2. PROPER TIES OF INC LUSIVE (n ,7 ) REACTIONS IN NUCLEIT. Bowles, D. F. Geesaman, R. J. Holt, H. E. Jackson, R. M.Laszewski, J. R. Specht, L. L. Rutledge, Jr. R. F. Segel,;R. P. Redwine,t and M. A. Yates-Williamst

Phys. Rev. L ctt. 40, 97 -99 (9 Janua ry 1978)

3. ENERGETIC CHARGED PARTICLE '(IELDS INDUCED BY PIONS ONCOMPLEX NUC LEI

H. E. Jackson, S. B. Kaufman, L. Meyer-Schutzmeister,J. P. Schiffer, S. L. Tabor, S. E. Vigdor, J. N. Worthington,L. L. Rutledge, Jr. , R. IE. Segel, R. L. Burmai, 1 P. A. M.Gram, .t P. Redwine,t and M. A. Yatest

Phys. Rev. C 16, 730-7410 (August 1977)

4. STUDY OF PION-ABSOR1TION MECHANISMS IN 4ie AND OTHERNUCLEI

I. 1. Jackson, S. L. Tabor, K. 1:. ,,hn, J. 1. Schiffer,R. E. Segel, L. L. Rutledge, Jr. , arnd M. A. Y atest

Phys. Rev. ILett. 39, 1601-160-1 (19 Decem ber 1977)

5. COMPARISON OF LIGHT T- AND -IEAVY -ION MISSION FROM TIHEl 2C+16 O S YSTIE M

S. L. Tabor, Y. Iisen, D. G. Kovar, and Z. VagerPhys. Rev. C 16, 673-678 (August 1977)

6. 6+48Ca REACTION AT 56 IV. 1. TRANSITIONS TO RESOLVEDLEVELS

D. G. Kovarit, W. Henning, 11. 7eidman, Y. His en, J. R. Erskine,11. T. Fo rtune, I'. R. Ophel, 1'. Sperr, and S. E. Vigdor

Phys. Rev. C 17, 83-110 (J;inuary 1978)

7. MASS AND BETA DECAY OF AsR. C. Pardo, C. N. Davids, M. J. Murphy, E. 13. Norman, andL. A. Pa rks

Phys. Rev. C 15, 1811 -1821 (M ay 1977)

8. MASS AND BETA DECAY OF MnR. C. Pardo, C. N. Davids, M. J. Murphy, 1K. B. Norman, andL. A. Parks

Phys. Rev. C 16, 370-378 (July 1977)

No rthweste rn Unive rsity, Evanston, Illinois.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

t Chemistry Division, ANL.

232

Publications

9. DESIGN AND OPERATION OF' A MULTIPLE RABBIT

Lewis A. Parks, Cary N. Davids, Bruce G. Nardi,* and

James N. Worthington

Nucl. Instrum. Methods 143, 93-97 (1977)

10. NUCLEAR REACTIONDennis G. Kovar

McGraw-Hill Yearbook of Science and Technology. 1977,edited by Daniel N. Lapedes (McGraw-Hill, Inc.,New York, 1977), pp. 313-315

a0i1. Ar(p,d) 'Ar REACTION AT Ep = 35 MeVJ. F. Tonn, R. E. Segel, J. A. Nolen,t W. S. Chien,t andP. T. Debevec

Phys. Rev. C 16, 1357-1362 (October 1977)

12. LOW-LYING STATES IN 39Ar FROM THE 7Cl(ad) 9Ar REACTION

J. F. Tonn, R. E. Segel, W. C. Corwin, and L. L. Rutledge, Jr. fPhys. Rev. C 16, 2065-2069 (November 1977)

13. GIANT ELECTRIC RESONANCES IN 58Ni STUDIED BY ALPHAPARTICLE CAPTURE

L. Meyer-Schtzrmeister, R. E. Segel, K. Raghunathan,P. T. Debevec, W. R. Wharton, L. L. Rutledge, and T. R. Ophel

Phys. Rev. C 17, 56-65 (January 1978)

14. ABSOLUTE CROSS SECTIONS FOR DEUTER ON-INDUCED REACTIONSON 6 Li AT ENERGIES BELOW i MeV

A. J. Elwyn, R. E. Holland, C. N. Davids, L. Meyer-Schutzmeister,J. F. Monahan, F. P. Mooring, and W. Raiy, Jr.

Phys. Rev. C 16, 1744-1756 (November 1977)

15. THERMONUCLEAR REACTION RATE PARAMETERS FOR d+ LiREAC TIONS

A. J. Elwyn, J. E. Monahan, and F. J. D. SerdukeNucl. Sci. Eng. 63, 343-346 (1977)

16. ENERGY LEVELS OF 239U OBSERVED WITH THE (d,p) REACTIONJohn R. Erskine

Phys. Rev. C 17, 934-938 (March 1978)

Electronics Division, ANL.

tMichigan State University, E. Lansing, Michigan.

tNorthwestern University, Evanston, Illinois.

233

Publications

17. SURVEY OF SINGLE-PARTICL E STATES IN THE MASS REGION

A > 228R. R. Chasman,: I. Ahrnad,* A. M. Friedman,* and J. R.Erskine

Rev. Mod. Phys. 49, 833-891 (October 1977)Erratum: Rev. Mod. Phys. 50 (Part I), 173 (January 1978)

18. ENERGY DEPENDENCE OF THE OPTICAL MODEL PARAMETERSFOR 3-ie IONS SCATTERED FROM 4 0 Ca AND 5 8 Ni

H. H. Chang,t B. W. Ridley,t T. H. Braid, T. W. Conlon,$E. F. Gibson, and N. S. P. King I

Nucl. Phys. A297, 105-124 (1978)

19. MAGNETIC MOMENT OF THE FIRST EXCITED STATE OF 43ScR. J. Mitchell, 9 T. V. Ragland, R. P. Scharenberg, 5 R. E.Holland, and F. J. Lynch

Phys. Rev. C 16, 1605-1608 (October 1977)

20. REVIEW OF "NUCLEAR ANALOGUE STATES, DONALD ROBSONAND JOHN D. FOX, EDS."

John P. SchifferAmerican Scientist 65(5), 628 (September-October 1977)

21. THIN CARBON FOIL BREAKAGE TIMES UNDER ION BEAMBOMBARDMENT

A. E. Livingston, H. G. Berry, and G. E. ThomasNucl. Instrum. Methods 148, 125-127 (1978)

22. EVIDENCE FOR COLLEC'1IVE M1 STRENGTH IN 208Pb BETWEEN8 AND 10 MeV

R. M. Laszewski, R. J. Holt, and H. E. JacksonPhys. Rev. Lett. 38, 813-816 (11 April 1977)

Chemistry Division, ANL.

tUniversity of Colorado, Boulde r, Colorado.*

A ER E Ha rwell, England.

Califo rnia State University, Sacramento, California.

II University of California, Davis, California.

Purdue University, West Lafayette, Indiana.

Halsted Press, 1976.

234

Publications

23. TABLE OF DIFFERENTIAL POLARIZATION COEFFICIENTS FOR(GAMMA, PARTICLE) REACTIONS

R. M. Laszewski and R. J. HoltAtomic Data and Nucl. Data Tables 19, 305-362 (April 1977)

24. A COMPARISON OF THE GAMMA-RAY SPECTRA FROM 2.8-keVNEUTRON CAPTURE AND THERMAL-NEUTRON CAPTURE IN

SODIUM -23W. M. Wilson, H. E. Jackson, and G. E. Thomas

Nucl. Sci. Eng. 63., 55 (May 1977)

25. ELECTROEXCITATION OF NON-NORMAL PARITY STATES IN ItBW. D. Teeters and D. Kurath

Nucl. Phys. A283, 1-11 (June 1977)

26. PROPERTIES OF THE d 3 / 2 -HOLE. STATES IN THE if 7 / 2 NUCLEIR. D. Lawson and A. Miller-Arnke'

Phys. Rev. C 16, 1609 -1616 (October 1977)

27. AXIAL CURRENTS IN NUCLEIKuniharu Kubodera, Jean Delorme,t and Mannque Rhot

Phys. Rev. Lett. 40, 755-758 (20 March 1978)

28. NUCLEAR MASS RELATIONS AND EQUATIONSJ. E. Monahan and F. J. 1). Serduke

Phys. Rev. C 17, 1196-1204 (Mrch 1978)

29. NUMERICAL COMPARISON OF TIIREE THEORIES OF NUCLEARMATTER

J. W. Clark, M. T. Johnson, P. N1. Lam, and J. G. ZabolitzkyNucl. Phys. A283, 253-268 (13 June 1977)

30. FERMI-HYPERNETTED-CHAIN METHODS AND THE GROUNDSTATE OF FERMION MATTER

John G. ZabolitzkyPhys. Rev. A 16, 1258- 1283 (September 1977)

Technische IIochschule, Darmstadt, Germany.

tUniversit Claude Bernard and Institut National de Physique Nucloaireet de Physique des Particules, Villeurbanne, France.

Centre d'Etudes Nucl~aire, Saclay, France.

Washington University, St. Louis, Missouri.

235

Publications

31. THOMAS FERMI MODEL OF FINITE NUCLEI

J. Boguta and Johann RafelskiPhys. Lett. 71B, 22-26 (7 November 1977)

32. RELATIVISTIC CALCULATION OF NUCLEAR MATTER AND THENUCLEAR SURFACE

J. Boguta and A. R. BodmerNucl. Phys. A292, 413-428 (5 December 1977)

33. THEORETICAL MOMENTUM DISTRIBUTIONS FOR LIQUID 3He

J. W. Clark,* P. M. Lam,* J. G. Zabolitzky, and M. L. Ristigt

Phys. Rev. B 17, 1 147 -1 151 (1 February 1978)

34. REMARKS ON CALCULATING THE PION-NUCLEUS FIRST-ORDER

OPTICAL POTENTIALT. -S. H. Lee

Phys. Lett. 67B, 282-284 (11 April 1977)

35. SECOND-ORDER PION-NUCL,.US OPTICAL POTENTIALTsung-Shung H. Lee and Soumya Chakravarti

Phys. Rev. C 16, 273-283 (July 1977)

36. MOLECULAR CONFIGURATIONS IN HEAVY -ION COLLISIONSH. Chandra* and U. Mosel

Nucl. Phys. A298, 151.-168 (27 March 1978)

37. CLASSICAL MICROSCOPIC CALCULATIONS OF HIGH-ENERGYCOLLISIONS OF HEAVY IONS

A. R. Bodmer and C. N. PanosPhys. Rev. C 15, 1342-1358 (April 1977)

38. PHOTODISSOCIATION: ISOTOPE EFFECTS AND COMPARISONSBETWEEN THEORY AND EXPERIMENT

Michael D. Morse, Karl F. Freed, and Yehuda B. BandChem. Phys. Lett. 49, 399-404 (1 August 1977)

39. ENERGY DISTRIBUTION IN SELECTED FRAGMENT VIBRATIONSIN DISSOCIATION PROCESSES IN POLYATOMIC MOLECULES

Yehuda B. Band and Karl F. FreedJ. Chem. Phys. 67, 1462-1472 (15 August 1977)

Washington University, St. Louis, Missouri.

tUniversitat zu Koln, Koln, Germany.

*Universitat Giessen, Giessen, Germany.

University of Chicago, Chicago, Illinois.

236

Publications

40. COHERENT-STATE MULTIPOLE MOMENTS: SOURCE OF IMPOR-TANT SCATTERING INFORMATION

Gerald Gabrielse and Yehuda B. BandPhys. Rev. Lett. 39, 697-700 (12 September 1977)

41. NUCLEAR-STRUCTURE EFFECTS IN PION DOUBLE CHARGE

EXCHANGE

T. -S. H. Lee, D. Kurath, and B. Zeidman

Phys. Rev. Lett. 39, 1307-1310 (21 November 1977)

42. COMMENT ON DISCUSSION BY FLOQUET AND LECTURE BY

HERSCHBAC HK. F. Freed,* M. D. Morse,' and Y. B. Band

Discuss. Faraday Soc. 62, 144-147 (1977)

43. DESIGN OF NATURAL COLLISION COORDINATES TO DESCRIBEDISSOCIATION OF POLYATOMIC MOLECULES

Yehuda B. Band and Karl F. Freed*

J. Chem. Phys. 68, 1292-1302 (1 February 1978)

44. COMPARISON OF SEMICLASSICAL TREATMENTS FOR EVALUATINGFRANCK-CONDON TRANSITION AMPLITUDES FOR MOLECULARDISSOCIATION

Yehuda B. Band, Michael D. Morse,* and Karl F. Freed*

J. Chem. Phys. 68, 2702-2709 (15 March 1978)

45. PRODUCT ENERGY DISTRIBUTIONS IN THE DISSOCIATION OFPOLYATOMIC MOLECULES

Karl F. Freed' and Yehuda B. Band

Excited States, Vol. 3, edited by E. Lim (Academic,New York, 1978), pp. 109-201

46. POSSIBLE EXPERIMENTAL TEST OF LOCAL COMMUTATIVITYPaul Beniofft and Hans Ekstein

Phys. Rev. D 15, 3563-3567 (15 June 1977) .

47. VIRIAL THEOREM AND STABILITY OF LOCALIZED SOLUTIONSOF RELATIVISTIC CLASSICAL INTERACTING FIELDS

Johann RafelskiPhys. Rev. D 16, 1890-1899 (15 September 1977)

University of Chicago, Chicago, Illinois.

tChemistry Division, ANL.

237

Publications

48. FERMIONS AND BOSONS INTERACTING WITH ARBITRARILY

STRONG EXTERNAL FIELDS

Johann Rafelski, Lewis P. Fulcher, * and Abraham KleintPhys. Lett. 38C(5), 227-361 (March 1978)

49. SOME CONSEQUENCES OF FERMI-TYPE THEORY OF WEAKINTERACTIONS

M. Danost and J. Rafelski

Nuovo Cimento Lett. 19(9), 339-343 (1977)

50. HIGHER-ORDER EFFECTS IN FERMI-TYPE CHARGED CURRENTTHEORY OF WEAK INTERACTIONS: SEMI-LEPTONIC NEUTRALCURRENTS

Michael Danos* and Johann RafelskiPhys. Lett. 73B, 313-316 (27 February 1978)

51. BOSE CONDENSATION IN SUPERCRITICAL EXTERNAL FIELDS.CHARGED CONDENSATES

Abraham Kleint and Johann Rafelski

Z. Phys. A 284, 71-81 (1978)

52. ISOSPIN RESTRICTIONS ON CHARGE DISTRIBUTIONS INCHARMED-PARTICLE DECAYS

Murray Peshkin and Jonathan L. Rosner

Nucl. Phys. B122, 144-169 (18 April 1977)

53. ARE THERE CHARMED-STRANGE EXOTIC MESONS?Harry J. Lipkin

Phys. Lett. 70B, 113-116 (12 September 1977)

54. A DYNAMICAL MODEL FOR MIXING OF AXIAL VECTOR (Q)ME SONS

Harry J. LipkinPhys. Lett. 72B, 249-250 (19 December 1977)

55. TWO-COMPONENT POMERON AND HADRON TOTAL CROSSSECTIONS AND REAL PARTS

Harry J. LipkinPhys. Rev. D 17, 366-368 (1 January 1978)

Bowling Green State University, Bowling Green, Ohio.

University y of Penns ylvania, Philadelphia, Pennsylvania.

t National Bureau of Standards, Washington, D. C.

Institute for Advanced Study, Princeton, New Jersey.

238

Publications

56. SPATIAL DISTRIBUTION OF ORIENTATION OF FAST IONS EXCITEDBY SURFACE-GRAZING COLLISIONS

H. G. Berry, G. Gabrielse, A. E. Livingston, R. M. Schectman,and J. Desesquelles

Phys. Rev. Lett. 38, 1473-1476 (20 June 1977)

57. MATERIAL-DEPENDENT VARIATIONS OF ALIGNMENT IN

BEAM-FOIL EXCITATION "H. G. Berry, G. Gabrielse, T. Gay,' and A. E. Livingston

Physica Scripta 16, 99-104 (September-October 1977)

58. ALIGNMENT OF HELIUM EXCITED BY THIN CARBON FOILS

R. D. Hight,t R. M. Schectman,t H. G. Berry, G. Gabrielse,'and T. Gay*

Phys. Rev. A 16, 1805-1810 (November 1977)

59. OPTICAL OBSERVATIONS OF THE DISSOCIATION OF FASTMOLECULES IN THIN FOILS

H. G. Berry, A. E. Livingston, and G. GabrielsePhys. Lett. 64A, 68-70 (28 November 1977)

60. PRODUCTION DF ORIENTATION AND ALIGNMENT IN HEAVY-ION-SURFACE COLLISIONS

H. G. Berry, G. Gabrielse, and A. E. LivingstonPhys. Rev. A 16, 1915-1928 (November 1977)

61. MEASUREMENT OF THE STOKES PARAMETERS OF LIGHTH. G. Berry, G. Gabriclse, and A. E. Livingston

Appl. Optics _6, 3200-3205 (December 1977)

62. MODIFICATION FOR SEALING DEPENDEX FITTINGS WITH COPPERR. Ekern

J. Vac. Sci. Technol. 14, 828-829 (May/June 1977)

63. A NEW APPROACH TO ASSESSING FUSION PLASMA -MATERIALSINTERACTIONS

F. Cafasso,$ D. Gruen, M. Kaminsky, J. E. Robinson, IIand H. Wiedersich9

Nucl. Technol. 34, 131-134 (July 1977)

University of Chicago, Chicago, Illinois.

tUniversity of Toledo, Toledo, Ohio.

*Chemical Engineering Division, ANL.

Chemistry Division, ANL.

l Solid State Science Division, ANL.

Materials Science Division, ANL.

239

Publications

64. SPUTTERING OF NIOBIUM BY ENERGETIC NEUTRONS AND

PROTONS: A ROUND-ROBIN EXPERIMENT

R. Behrisch, O. K. Harling,t M. T. Thomas,t R. L.Brodzinski,t L. H. Jenkins,* G. J. Smith,* J. F. Wendelken,*M. J. Saltmarsh,* M. Kaminsky, S. K. Das, C. M. Logan,R. Meisenheimer J. E. Robinson, I M. Shimotomai, I andD. A. Thomrpsonf'

J. Appl. Phys. 48, 3914-3918 (September 1977)

65. JOINT WORK ON SURFACE DAMAGE OF NiS. K. Das, M. S. Jaminsky, M. I. Guseva, 1 V. M. Gusev,Yu. L. Krasulin, Yu. V. Martynenko, T and I. A. Rozina5

Fiz. Khim. Obrab. Mater. [Phys. Chem. Mater.

Processing], No. 5, 94-99 (1977)

66. TEMPERATURE DEPENDENCE OF HELIUM BLISTERING INNICKEL MONOCRYSTALS

M. K. Sinha, S. K. Das, and M. Kaminsky

J. Appl. Phys. 49, 170-172 (January 1978)

67. COMPETITION BETWEEN AUTOIONIZATION AND RADIATIVE

EMISSION IN THE DECAY OF EXCITED STATES OF THE OXYGENATOM

P. M. Dehmer,', W. L. Luken,tt and W. A. ChupkaJ. Chem. Phys. 67, 195-203 (1 July 1977)

68. PHOTOIONIZATION OF N 2 0: MECHANISMS OF PHOTOIONIZATIONAND ION DISSOCIATION

J. Berkowitz and J. H. D. ElandJ. Chem. Phys. 67, 2740-2752 (15 September 1977)

Max-Planck-Institut fir Plasmaphysik, Garching/Munich, Germany.

tPacific Northwest Laboratory of the Battelle Memorial Institute,Richland, Washington.

$Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Lawrence Livermore Laboratory, Livermore, California.

IIMcMaster University, Hamilton, Ontario, Canada.

Kurchatov Institute of Atomic Energy, Moscow, USSR.

Radiological and Environmental Research Division, ANL.

ttDuke University, Durham, North Carolina.

240

Publications

+, 2 +69. FORMATION AND PREDISSOCIATION OF C0 2(C )

John H. D. Eland and Joseph Berkowitz

J. Chem. Phys. 67, 2782-2787 (15 September 1977)

70. PHOTOIONIZATION MASS SPECTROMETRY OF HI AND DI AT

HIGH RESOLUTION

J. H. D. Eland and J. Berkowitz

J. Chem. Phys. 67, 5034-5039 (1 December 1977)

71. ELECTRONIC STRUCTURES OF FULVALENE AND OCTACHLORO-

FULVALENE

D. G. Streets and J.. Berkowitz

Chem. Phys. 23, 79-85 (1977)

72. HYPERFINE -STRUCTURE AND ISOTOPE-SHIFT MEASUREMENTS

ON Dy I X5988. 562 USING HIGH-RESOLUTION LASER SPEC-TROSCOPY AND AN ATOMIC BEAM

W. J. Childs and L. S. GoodmanJ. Opt. Soc. Am. 67, 747 -751 (June 197')

73. COMPLETE RESOLUTION OF HYPERFINE STRUCTURE IN THE

CLOSE DOUBLET X5930.6 OF 1 3 9 La BY LASER-ATOMIC-BEAM

SPECTROSCOPY

W. J. Childs and L. S. Goodman

J. Opt. Soc. Am. 67, 1230-1234 (September 1977)

74. LASER-RF DOUBLE-RESONANCE MEASUREMENT OF THEQUADRUPLE MOMENTS OF 9 5 Mo AND 9 7 Mo

M. Dubke,= W. Jitschin,* G. Meisel, and W. J. ChildsPhys. Lett. 65A, 109-112 (20 F bruary 1978)

75. ANISOTROPY OF THE DEBYE-WALLER FACTOR IN CESIUM-GRAPHITE INTERCALATION COMPOUNDS BY MOSSBAUERSPEC TROSCOPY, AND THE QUADRUPOLE MOMENT OF THE

81-keV STATE IN 1 3 3 CsL. E. Campbell, G. L. Montet,t and G. J. Perlow

Phys. Rev. B 15, 3318-3324 (1 April 1977)

76. INTRODUCTIONS. L. Ruby

Chap. 1 in Mossbauer Isomer Shifts, edited by G. K.Shenoy and F. E. Wagner (North-Holland, Amsterdam,1978), pp. 1-14

Universitat Bonn, Bonn, West Germany.

tEnvironmental Impact Studies Division, ANL.

241

Publications

77. THE 5s-5p ELEMENTS BEYOND TIN: (Sb, Te, I, Xe)

S. L. Ruby and G. K. Shenoy*

Chap. 9b in Mossbauer Isomer Shifts, edited by G. K.

Shenoy and F. E. Wagner (North-Holland, Amsterdam,1978), pp. 617-659

78. QUANTUM BEATS OF RECOIL-FREE y RADIATION

Gilbert J. Perlow

Phys. Rev. Lett. 40, 896 -899 (27 March 1978)

79. SOME PROPOSED IMPROVEMENTS IN T HE SCANNING ION

MICROPROBE

V. E Krohn and G. R. RingoJ. Microscopy (Oxford) 110, 59-64 (May 1977)

C. PUBLISHED REPORTS AT MEETINGS

Proceedings of the Fourth International Symposium on Polarization

Phenomena in Nuclear Reactions, Zurich, Switzerland, 25-29 August

1975, edited by W. Griebler and V. Konig (Birkhiuser Verlag Basel, 1976)

1. POLARIZATION OF PHOTONEUTRONS FROM THE

THRESHOLD REGION OF 2 0 8 PbR. J. Holt and H. E. Jackson

pp. 759-760

Japan-United States Joint Seminar on "Quantitative Technique's in

Secondary Ion Mass Spectrometry," Honolulu, Hawaii, 12-17 October 1975

(University of Illinois, 1978)

2. ION-SURFACE INTERACTIONS: EXPERIMENTALM. Kaminsky

pp. 11-12

Conference on Experimental Quantum Mechanics, Erice, Italy, 18-23April 1976

3. A PROPOSED EXPERIMENT TO MEASURE SPIN CORRELA-TIONS IN PROTON-PROTON SCATTERING AT ALL AZIMUTHS

R. RingoProgress in Scientific Culture 1(4), 454 (Winter 1976)

Solid State Science Division, ANL and Centre de Recherches Nucldaires,Strasbourg, France.

242

Publications

Proceedings of the Conference on the Physics of Tandem and Nuclear

Physics Workshop, Trieste-Legnaro, Italy, 27 April-7 May 1976

4. HEAVY ION REACTIONSB. Zeidman

Nucl. Instrum. Methods 146, 199 -211 (1 October 1977)

Inelastic Ion-Surface Collisions (Proceedings of the Bell Laboratories

International Workshop Conference, Murray Hill, New Jersey, 28-30

July 1976), edited by N. Tolk (Academic, New York, 1977)

5. ORIENTATION AND ALIGNMENT IN BEAM TILTED-FOIL

SPECTROSCOPYH. G. Berry

pp. 309-327

Proceedings of the Faculty Institute on Curriculum Development in

Fusion-First Wall Design Considerations, Argonne National Laboratory,9-13 August 1976, edited by G. H. Miley and W. H. Sawyer (Center forEducational Affairs, Argonne, Illinois, 1977)

6. METHODS TO REDUCE SURFACE EROSION CAUSED BYRADIATION BLISTERING

S. K. Das and M. Kaminsky

Vol. II, Chap. 2, pp. 2-1-2-14

7. BLISTERING PHENOMENA I: METALS AND ALLOYSM. Kaminsky and S. K. Das

Vol. I, Chap. 12, pp. 12-1 -12-30

Fifth Annual Conference of the International Nuclear Target Development

Society, Los Alamos, New Mexico, 19-21 October 1976, compiled byJ. C. Gursky and J. G. Povelites (National Techn cal Information

Service, Springfield, Va. , June 1977), LA-6850-C

8. PRODUCTION OF1 FRACTIONAL ATOMIC LAYER STANDARDSOF NIOBIUM AND VANADIUM

G. E. Thomas and P. J. Dusza

pp. 164-175

1976 Nuclear Science Symposium and Scintillation and SemiconductorCounter Symposium-1976 Symposium on Nuclear Power Systems,New Orleans, Louisiana, 20 -22 October 1976

9. A COMMAND LANGUAGE BASED DATA-ACQUISITION ANDANALYSIS SYSTEM FOR LOW ENERGY PHYSICS

John W. Tippie* and Joseph E. KulagaIEEE Trans. Nucl. Sci. NS-24(1), 492-496(February 1977)

Applied Mathematics Division, ANL.

243

Publications

Program of the Sixth Annual Symposium on Applied Vacuum Science and

Technology, Tampa, Florida, 14-16 February 1977 (American Vacuum

Society, 1977)

10. SURFACE EROSION AND PLASMA CONTAMINATION IN

FUSION REACTORSS. K. Das and M. Kaminsky

pp. 14-15

Workshop on Short Wavelength Microscopy, New York, New York,23-25 February 1977

11. THE FEASIBILITY OF ACHIEVING 15-nm RESOLUTION WITH

A SCANNING MICROPROBE USING A LIQUID GALLIUM ION

SOURCE

V. E. Krohn and G. R. Ringo

Ann. N.Y. Acad. Sci. 306, 200-202 (1978)

Proceedings of the 1977 Particle Accelerator Conference-Accelerator

Engineering and Technology, Chicago, Illinois, 16-18 March 1977

12. TELEMETRY COMPONENT TESTS IN THE FN TANDEMTERMINAL

J. J. Bicek, P. J. Billquist, and J. L. YntemaIEEE Trans. Nucl. Sci. NS-24(3), i182-1183

(June 1977)+ Bull. Am. Phys. Soc. 22, 154 (February 1977)

13. SUPERCONDUCTING HEAVY -ION LINACSLowell M. Bollinger

IEEE Trans. Nacl. Sci. NS-24(3), 1076-1080

(June 1977)

14. PELLET FUSION BY HIGH ENERGY HEAVY IONSR. Burke,' Y. Cho,t J. Fasolo,t S. Fenster,t M. Foss,tT. Khoe,t A. Langsdorf, and R. Ma rtint

IEEE Trans. Nucl. Sci. NS-24(3), 1012-1014(June 1977)

15. SPLIT RING RESONATOR FOR THE ARGONNE SUPER-CONDUCTING HEAVY ION BOOSTER

K. W. Shepard, C. H. Scheibelhut, R. Benaroya,*and L. M. Bollinger

IEEE Trans. Nucl. Sci. NS-24(3), 1147-1149(June 1977)+ Bull. Am. Phys. Soc. 22, 152 (February 1977)

Engineering Division, ANL.

tAccelerator Research Facilities Division, ANL.

*Chemistry Division, ANL.

244

Publications

American Physical Society, Washington, D. C., 25-28 April 1977

16. ANALYSIS OF FLUORESCENCE PATTERN FROM

Dy X 5988. 562 USING HIGH-RESOLUTION LASER SPEC-

TROSCOPY AND AN ATOMIC BEAM

W. J. Childs and L. S. GoodmanBull. Am. Phys. Soc. 22, 558 (April 1977)

17. THE FUSION OF 160+ 40CaD. F. Geesaman, K. Daneshvar, C. N. Davids, W.

Henning, D. G. Kovar, K. E. Rehm, J. P. Schiffer,S. L. Tabor, B. Zeidman, and F. W. Prosser, Jr.:

Bull. Am. Phys. Soc. 22, 630 (April 1977)

18. MAXIMUM FUSION CROSS SECTIONS FOR 14N + 12C AND

'1 5 N + 12.C

W. Henning, D. F. Geesaman, D. G. Kovar, K. E.Rehm, J. P. Schiffer, and S. L. Tabor

Bull. Am. Phys. Soc. 22, 629 (April 1977)

1619. TRANSFER REACTIONS INDUCED BY 0 IONS AT Elab = 75

MeV ON 4 0 CaD. G. Kovar, K. Daneshvar, P. Sperr, and S. E. Vigdor

Bull. Am. Phys. Soc. 22, 564 (April 1977)

20. PROTON SCATTERING FROM 58,60,62,64Ni AT 800 MeV

G. Kyle,t G. Blanpied,* J. Fong, G. Fricke, IN. Hintz,t G. Hoffmann, T. Kozlowski,t P. Lang,

1R. Liljestrand,': D. Madland,t D. McDanielstt

C. Morris,* M. Oothoudt,t J. Pratt,* R. Ridge,K. Seth, 9 J. Spencer,* N. Tanaka,* H. Thiessen,*P. Varghesc,tt C. Whitten, and B. Zeidman

Bull. Am. Phys. Soc. 22, 561 (April 1977)

University of Kansas, Lawrence, Kansas.

University of Minnesota, Minneapolis, Minnesota.

tLos Alamos Scientific Laboratory, Los Alamos, New Mexico.

University of California, Los Angeles, California.

IIUniversity of Mainz, Mainz, Germany.

gNorthwestern University, Evanston, Illinois.

University of Texas, Austin, Texas.

ttUniversity of Oregon, Eugene, Oregon.

245

Publications

APS, Washington, April 1977 (Contd.)

21. GAMMA DECAY AND LIFETIME MEASUREMENTS OF THE

ISOMERIC 19/2~ STATE IN 4 3 TiL. Meyer-Schuitzmeister, G. Hardie, A. J. Elwyn, andK. E. Rehm

Bull. Am. Phys. Soc. 22, 527 (April 1977)

22. ENERGY DEPENDENCE OF THE ONE-PROTON AND ONE-NEUTRON TRANSFER REACTIONS INDUCED BY 160 ON208Pb

C. Olmer,' M. C. Mermaz,= M. Buenerd,' C. K.

Gelbke, D. L. Hendrie,* J. Mahoney,,; A. Menchaca-Rocha,* D. K. Scott,. M. H. Macfarlane, and S. C.

Pieper

Bull. Am. Phys. Soc. 22, 593 (April 1977)

23. CHANNELING OF 70. 5-MeV AND 255-MeV T AND Tr IN A

Si CRYSTALW. J. Pictsch, D. S. Gemmell, R. E. Holland, A. J.Ratkowski, J. P. Schiffer, T. P. Wangler, J. N.Worthington, B. Zeidman, C. L. Morris,t andH. A. Thiessent

Bull. Am. Phys. Soc. 22, 624 (April 1977)

24. STUDY OF THE 86Sr(a,y) REACTION IN THE GIANTRESONANCE REGION

K. Raghunathan, L. L.. Rutledge, Jr., R. E. Segel,and L. Meyer-Schfltzmeister

Bull. Am. Phys. Soc. 22, 542 (April 1977)

25. INELASTIC SCATTERING OF 60 ON THE EVEN CaISOTOPES 4 0 , 4 2 , 4 4 , 4 8 Ca

K. E. Rehm, J. Erskine, W. Henning, D. G. Kovar,M. Macfarlane, and Steven C. Pieper

Bull. Am. Phys. Soc. 22, 564 (April 1977)

26. ELASTIC SCATTERING OF 12C ON Ca ISOTOPEST. Renner and J. P. Schiffer

Bull. Am. Phys. Soc. 22, 563 (April 1977)

Lawrence Berkelei,' Laboratory, Berkeley, California.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

246

Publications

APS, Washington, April 1977 (Contd. )

27. SYSTEMATICS OF 0 + M g FUSIONS. L. Tabor, D. F. Geesaman, W. Henning, D. G.

Kovar, K. E. Rehm, and F. W. Prosser, Jr.-

Bull. Am. Phys. Soc. 22, 630 (April 1977)

Weak Interaction Physics-1977 (Proceedings of tht Conference, Indiana

University, Bloomington, 16-17 M\lay 1977), edited by ). 13. Lichtenberg(American Institute of Physics, New York, 1977), AIP ConferenceProceedings No. 37

28. PRESENT STATUS OF W EAK MAGNETISM AND SECOND-CLASS CURRENTS IN NUCLEAR BETA DECAY

G. T. Garveypp. 104-124

Tenth Midwest Theoretical Chemistry Confc rence, A rgonne National

Laboratory, Argonne, Illinois, 27-28 May 1977

29. EVALUATION OF FRANCK-CONDON FACTORS FORPOLYATOMIC MOLECULAR DISSOCIATION PHENOMENA

Yehuda B. Band, Michael D. Morse,t and Karl F. FreedtProgram and Abstracts, p. 20

30. PHOTOFRAGMENT ROTATIONAL POPULATION DISTRI-BUTIONS

Michael D. Morse,t Karl F. Freed,t and Yehuda B. BandProgram and Abstracts, p. 57

25th Annual Conference on Mass Spectrometry and Allied Topics,Washington, D.C., 29 May-3 June 1977 (ASMS, 1977)

31. THE CO2 DISSOCIATION PROBLEMJ. H. D. Eland and J. Berkowitz

Procc edings, pp. 493-495

+ Program of the Conference, Abstract A2

University of Kansas, Lawrence, Kansas.

tUniversity of Chicago, Chicago, Illinois.

247

Publications

Workshop on New Directions in Mossbauer Spectroscopy (Argonne 1977),Argonne, Illinois, 10-11 June 1977, edited by Gilbert J. Perlow/American Institute of Physics, Inc. , New York, 1977), AIP Conference

Proceedings No. 38

32. PANEL DISCUSSION ON USES OF SYNCHROTRON RADIATIONR. L. Cohen,' P. A. Flinn, E. Gerdau,t J. P. Hannon,S. L. Ruby, and G. T. Trammell*

pp. 140-148

33. COHERENCE AND INT ERFERENC E IN THE MOSSBAUEREFFECT

Ha rry J. Lipkin

pp. 63-71

34. COMMENT TO THE PAPIER OF HOY, C-APPERT, ANDBENSKI

Murray PHshkin

p. 76

35. SYMMETRIC RADIANT STATE IN NUCLEAR RESONANTBRAGG SCATTERING

S. L. Ruby

pp. 50-54

36. COI-IERENT NUCLEAR SCATTERING OF SYNCHROTRONRADIATION

G. T. Trammell,t' J. P. Hannon, S. L. Ruby, Paul Flinn,R. L. Mossbauer, and F. Parak

pp. 46-49

Proceedings of th( Topical Conference on Heavy-Ion Collisions,Fall C reek Falls State Pa rk, Pikeville, Tennessee, 13-17 June 1977,organized by 1,. C. Halbert et al. (Oak Ridge National Laboratory,October 1977), CONF-770602

37. MICROSCOPIC DESCRIPTIONS OF HIGH-ENERGY HEAVY -ION COLLISIONS

A. R. Bodmer

pp. 309-362

Bell Laboratories, Murray Hill, New Jersey.

tUniversitit Hamburg, Hamburg, Germany.

Rice University, Houston, Texas.

Technische Universitat Munchen, Munchen, Germany.

248

Publications

Heavy-Ion Collisions, Pikeville, Tenn., June 1977 (Contd.)

38. R ELATIVISTIC EQUATIONS-OF-MOTION CALCULATIONS OF

HIGH-ENERGY HEAVY -ION COLLISIONSA. R. Bodme r, A. D. Ma cKella r, and C. N. Panos

p. 479

1977 Canadian Association of Physicists Conijr ess, Sa skatoon, Canada,20 -23 June 1977

39. ORIENTATION OF' FAST IONS lXCI I ED BY GRAZING

SURFACE COLLISIONSH. G. Berry, G. Gabrielse, and A. 1,. Livingston

Bull. Can. Assoc. Phys. 33(3), 27 (1977)

Third International Conference on Ion F> nn Anll'I ysi s , Wa shington, D. C.,27 June -1 July 1977

40. ORIENTATION OF FAST IONS EXCITED IN SURFACE

COLLISIONSH. G. Berry, G. Gabri else, and A. I. Livingston

Nucl. Iristrom. Methods 149, 517 -522 (15 February -

I March 1978)+ Program of the (ofe relc e, organized by The

Naval Research Laboratory and Georgetown

University (1977), p. 128

41. POSSIBLE APPLICATIONS OF A HIGH BRIGH-ITNE:SS

GALLIUM SOUR CE TO ION MIC ROP ROBES

G. R. Ringo and V. I. KrohnNucl. Instrum. Methods 149, 735 -737 (15 February -1 March 1978)+ Program of the Conference, 1). 122

ICPFAC 10th International Conference on the Physics of Electronic and

Atomic Collisions, Paris, France, 21-27 July 1977 (Coinmissariat a

l' Energie Atomique, Paris, 1977), Vol. 1, Abstracts of Papers

42. PHOTOIONIZATION OF N 2 0: MECHANISMS OF DISSOCIATIVEIONIZATION

J. Berkowitz and J. H. D. Eland

p. 110

Proceedings of SHARE 49, Washington, D. C., 21-26 August 1977(SHARE, Inc. , 1977)

43. HUMAN FACTORS IN SPEAKEASYStan Cohen

Vol. III, pp. 2010 -2012

249

Publications

174th American Chemical Society Meeting, Division of Nuclea r

Chemistry and Technology, Chicago, Illinois, 29 August-2 September 1977

44. NEW ISOTOPES IN THE f-p SHELL PRODUCED BY HEAVY-

ION REACTIONSCary N. Davids

Abstracts of Papers, Abstract NUCL 37

Proceedings of the 7th International Conference on High-Energy Physics

and Nuclear Structure, Zurich, Switzerland, 29 August-2 September 1977

(SIN-Swiss Institute for Nuclear Research, Villigen, Switzerland, 1977)

45. GAMMA-RAY STUDY OF PION-INDUCED REACTIONS ON

COMPLEX NUCLEIH. E. Jackson, S. B. Kaufman,' L. Meyer-Schutzmeister,

J. P. Schiffer, R. E. Segel, S. E. Vigdor, L. L.Rutledge, R. L. Burman, t P. A. M. Gram,t R. P.Redwine,t M. A. Yates,t and S. L. Tabor

Abstract Volume, p. 90

46. ENERGETIC CHARGED PARTICLE YIELDS INDUCED BYPIONS ON COMPLEX NUCLEI

H. E. Jackson, S. B. Kaufman, L. Meyer-Schutzmeister,J. P. Schiffer, S. L. Tabor, S. E. Vigdor, J. N.Worthington, L. L. Rutledge, R. E. Segel, R. L. Burman,t

P. A. M. Gram,t R. P. Redwinet and M. A. YatestAbstract Volume, p. 16

47. INITIAL R ESU LTS WITH EPICS PION SPEC TROM EFTE RSYSTEM

H. A. Thiessen,t J. F. Amann,* P. D. Barnes,* R.Boudrie, K. Boyer, I W. J. Braithwaite, I G. R.Burleson, 1 R. A. Eisenstein,t S. Ive rson, J. J.Kraushaar, , C. F. Moore, C. L. Morris,t A, Obst,R. J. Peterson, R. A. Ristinen, K. K. Seth, E.Smith,t S. Sobottka,tt L. W. Swenson,*t N. Tanaka,tM. D. Thomason,t P. Varghese, S. Verbeck,T andB. Zeidman

Abstract Volume, p. 375

Chemistry Division, ANL.

t Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

*Carnegie-Mellon University, Pittsburgh, Pennsylvania.

University of Colorado, Boulder, Colorado.

I University of Texas, Austin, Texas.

5New Mexico State University, Las Cruces, New Mexico.

-"Northwestern University, Evanston, Illinois.

ttUniversity of Virginia, Charlottesville, Virginia.

* Oregon State University, Corvallis, Oregon.

University of Oregon, Eugene, Oregon.

250

Publications

Proceedings of the IPCR Symposium on Macroscopic Features of Heavy-Ion

Collisions and Pre-equilibrium Process, Hakone, Japan, 2-3 September

1977, edited by H. Kamitsubo and M. Ishihara (The Institute of Physicaland Chemical Research, December 1977), IPCR Cyclotron Progress

Report Supplement 6

48. MICROSCOPIC-MACROSCOPIC FEATURES IN FUSION

REACTIONS INVOLVING LIGH IT YST V MSD. G. Kova r

pp. 18-77

International Conference on Low-Einrg- Too In ;ims, So ford, England,5-8 Septer-ber 1977

49. AN ACCELERATOR SYSTI'M FOIE PIR(ODUCING TWO-COMPONENT BEAMS FIO1 STUDIO VS OF IN VERACTIVF

SURFACE EFFECTS ;

M. Kaminsky, S. K. Da s, R. Eke rn, and ). (. Hess

Inst. Phys. Conf. Ser . No. 38 (Proc eedings ofthe Conference) (Institute of Phy sics, London, 1978),Chap. 7, pp. 305-312

24th International Field Ernission Symposioinm, Oxford, England, 5-9

September 1977

50. CURRENT-VS-VOLTAGE CHARACTERISTICS FOR THEFIELD EVAPORATION OF IONS FROM A LIQUID-METAL

CONE

V. F. KrohnProgram of the Symposium, p. 48

Proceedings of the International Conference on Nuclear Structure,Tokyo, Japan, 5-10 September 1977

51. REACTION MECHANISM STUDIES OF PIONS ON COMPLEXNUCLEI

H. Jackson, S. Kaufman,' L. Meyer-Schutzmeister,J. Schiffer, S. Tabor, S. Vigdor, J. Worthington, L.

Rutledge,t R. Segel, R. Burman,+ P. Gram, * R.

Redwine,T and M. Yatest

Contributed Papers (Organizing Committee of

International Conference on Nuclear Structure,August 1977), p. 811

Chemistry Division, AN L.tNorthwestern University, Evanston, Illinois.

Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

251

Public ations

International Conference on Nuclear Structure, Tokyo, Sept. 1977 (Contd. )

52. FUSION CROSS SECTION BEHAVIOR FOR LIGHT SYSTEMS

D. G. Kovar, K. Daneshvar, D. F. Geesaman, W. Henning,

F. W. Prosser, Jr., K. E. Rehm, J. P. Schiffer, and

S. L. 'laborContributed Papers (Organizing Committee of

International Conference on Nuclear Structure,

August 1977), p. 660

53. INELASTIC SCATTERING OF 160 ON EVEN-Ca ISOTOPES

K. E. Rehm, J. R. Erskine, W. Henning, D. G. Kovar,M. H. Macfarlane, and Steven C. Pieper

Contributed Papers, p. 609

54. INTRODUCTORY TALK

J. P. SchifferJ. Phys. Soc. Japan Suppl. 44, 9-26 (1978)Invited Papers, edited by T. Marumori (Physical

Society of Japan, 1978)

55. COULOMB EXCITATION IN EVEN-N Sm NUCLEI

R. K. Smither, I. Ahmad, A. M. Friedman, and1). L. Bushnellt

Contributed Papers, p. 377

56. ENERGY LEV ELS IN 155SrRobert K. Smither, K. Schreckenbach, A. I. Namenson, I

W. F. Davidson,* H. G. 3orner,* J. A. Pinston, 4" D. D.

Warner, 4 T-. V. Egidy, t rind W. StofflContributed Papers, p. 393

Proceedings of the Seventh International Vacuum Congress and the Third

International. Conference on Solid Surfaces, Vienna, Austria, 12-16

September 1977, edited by R. Dobrozemsky, F. R~idenauer, F. P.

Viehbock, and A. Breth (R. Dobrozemsky et al., Vienna, 1977)

57. THE WALL PROBLEM IN FUSION DEVICESM. Kaminsky

Vol. III, p. A-2716

Chemistry Division, ANL.

tNorthern Illinois University, DeKalb, Illinois.

Institute Laue-Langevin, Grenoble, France.

Technical University of Munich, Munich, Germany.

252

Publications

Proceedings of the 1977 Annual Conference of the Association for

Computing Machinery (ACM 77), Seattle, Washington, 16-19 October 1977(Association for Computing Machinery, New York, 1977)

58. SPEAKEASY LINKULES - PLUG COMPATIBLE SOFTWARE

Stan Cohen

pp. 419-424

Prograrn of the 1977 TMS-AIME Fall MIttitig, Chica go, Illinois, 24-27

October 1977 (Metallurgical Society of AIMR, New York, 1977)

59. DEPTH DISTRIBUTION OF HELIUM BUBBLES IN 4IHL -IONIRRADIATED NICKEL

G. Fenske, S. K. Das, and M. Kaninskyp. 10

Proceedings of the Symposium on Heavy-Ion Elastic Scattering, Rochester,New York, 25-26 October 1977, organized by J. G. Cramer, R. N.DeVries, J. R. Huizenga , M. -1. Macfarlane , ;-nd G. R. Stchler

(University of Rochester, 1978)

60. ELASTIC SCATTERING OF IDIENTICAL. ION: S2S 32S AND4 0Ca + 4 0 Ca

W. Henning

pp. 166-209

61. THE TARGET DEPENDENCE OF HEAVY-ION ELASTICSCATT RING

M. H. Macfarlane and S. C. Pieper

pp. 327-362

62. 16 40Ca INELASTIC SCATTERING AND THE ELASTICSCATTERING WAVE FUNCTION

K. E. Rehm, W. Henning, J. R. Erskine, and D. G. Kovar

pp. 516-518

American Physical Society, Division of Nuclear Physics, Rochester,New York, 27-29 October 1977

63. PION SINGLE CHARGE EXCHANGE AT 100 M eVT. J. Bowles, D. F. Geesaman, R. J. Holt, H. E.

Jackson, R. Laszewski, T. S. H. Lee, L. Rutledge,'R. E. Segel, R. Redwine,t and M. A. Yatest

Bull. Am. Phys. Soc. 22, 1007 (September 1977)

Northwestern University, Evanston, Illinois.

tLos Alamos Scientific Laboratory, Los Alamos, New Mexico.

253

254 Publications

APS, Rochester, October 1977 (Contd.)

64. INDUCED WEAK CURRENTS IN NUCLEAR BETA DECAY,A = 8

G. T. Garvey

Bull. Am. Phys. Soc. 22, 1001 (September 1977)

65. THE FUSION OF 13C + 12C

D. F. Geesaman, W. Henning, D. G. Kovar, K. E. Rehrn,

J. P. Schiffer, and S. L. TaborBull. Am. Phys. Soc. 22, 1019 (September 1977)

66. DIRECT AND RESONANCE PHOTONEUTRON REACTIONS

IN 170

R. J. Holt, R. M. Laszewski, H. E. Jackson, and

J. E. Monahan

Bull. Am. Phys. Soc. 22, 1021 (September 1977)

67. INELASTIC SCATTERING OF aT AND n FROM 180 AT 140

AND 230 MeV

S. Iverson,- A. Obst,* K. K. Seth, H. A. Thiessen,t

C. L. Morris, N. Tanakat E. Smith,t D. Madland,tJ. F. Amann,t R. Boudrie, D. Dehnha rd, II G. Burleson, 9M. Devereux, y S. Verbeck, W. Swenson, P. Varghese,

B. Zeidman, K. Boyer," W. J. Braithwaite,tt

S. Greene," W. Cottingame,tt L. Eugene Smith," and

C. Fred Moorett

Bull. Am. Phys. Soc. 22, 1007 (September 1977)

68. ABSORPTION M- CHANISM STUDIES OF ENERGETIC PIONSIN NUC LEI

H. E. Jackson, K. E. Rehm, L. L. Rutledge, Jr.,J. P. Schiffer, R. E. Segel, S. L. Tabor, and -M. A.Yatest

Bull. Am. Phys. Soc. 22, 1006 (September 1977)

Northwestern University, Evanston, Illinois.

tLos Alamos Scientific Laboratory, Los Alamos, New Mexico.

Ca rnegie -Mellon University, Pi"-sburgh, Pennsylvania.

University of Colorado, Boulder, Colorado.

I University of Minnesota, Minneapolis, Minnesota.

New Mexico State University, Las Cruces, New Mexico.

Oregon State University, Corvallis, Oregon.

ttUniversity of Texas, Austin, Texas.

Publications

APS, Rochester, October 1977 (Contd.)180 + 180

69. ON THE PRODUCTION OF Ta(8 g. s.) BY THE Hf(p,n)180Ta REACTION

E. B. Norman, T, R. Renner, and J. P. Schiffer

Bull. Am. Phys. Soc. 22, 1032 (September 1977)

70. STRUCTURE IN THE FUSION OF 160 1 O

J. P. Schiffer, D. F. Geesaman, W. Henning, D. G.

Kovar, K. E. Rehm, S. L. Tabor, F. W. Prosser, Jr.,-

J. V. Maher,t and W. JordantBull. Am. Phys. Soc. 22, 1019 (September 1977)

71. RADIOACTIVITIES PRODUCED BY PION BOMBARDMENT

OF NICKEL ISOTOPESM. A. Yates, H. E. Jackson, K. E. Rehm, L. L.

Rutledge, Jr. , J. P. Schiffer, R. E. Segel, and S. L.Tabor

Bull. Am. Phys. Soc. 22, 1006 (September 1977)

24th National Vacuum Symposium of American Vacuum Society, Boston,Massachusetts, 8-11 November 1977

72. SURFACE DAMAGE OF MOJLYBI)ENUM AND TZM ALLOYUNDER D+ IMPACT

S. K. Das, M. Kaminsky, and P. Dusza

J. Vac. Sci. Technol. 15, 710-713 (March/April1978)

1977 Fall Decus U. S. Symposium, San Diego, California, 28 November-1 December 1977

73. DATA ACQUISITION AND EXPERIMENT CONTROL VIACAM AC

Joseph E. Kulaga and John W. Tippie

Proceedings of the Digital Equipment Computer Users

Society, Vol. 4, No. 2, USA Fl 1977, edited by

Fred Strange (Digital Equipment Corp. , Maynard,Mass. , 1978), pp. 597-600+ Program of the Conference, p. xiv

University of Kansas, Lawrence, Kansas.

University of Pittsburgh, Pittsburgh, Pennsylvania.tLos Alamos Scientific Laboratory, Los Alamos, New Mexico.

Northwestern University, Evanston, Illinois.

Applied Mathematics Division, AN L.

255

Publications

American Physical Society, Division of Electron and Atomic Physics,Knoxville, Tennessee, 5-7 December 1977

74. CALCULATION OF HYDROGEN COHERENCE MULTIPOLESPRODUCED BY ELECTRON IMPACT

Yehuda Band and Gerald GabrielseBull. Am. Phys. Soc. 22, 1312 (1 December 1977)

75. HYPERFINE STRUCTURE OF d 2p AND dsp LEVELS IN 139LaBY HIGH-RESOLUTION LASER SPECTROSCOPY AND ANATOMIC BEAM

W. J. Childs and L. S. Goodma n

Bull. Am. Phys. Soc. 22, 1317 (1 December 1977)

76. OPPOSITE PARITY COHERENCE IN THIN FOIL EXCITATION

OF HYDROGEN n 2

G. GabrielseBull. Am. Phys. Soc. 22, 1320 (1 December 1977)

77. AN INTUITIVE PICTURE OF THE COHERENT EXCITATIONOF HYDROGEN BY ELECTRON IMPACT: WHY PLANEWAVE AND DISTORT TED WAVE BORN APPROXIMATIONSARE INAPPROPRIATE

Gerald Gabrielse and Yehuda BandBull. Am. Phys. Soc. 22, 1312 (1 Dec(mber 1977)

78. FINE STRUCTURE OF THE Is2s2p PO AND ls2p2 4PSTATES IN LITHIUM-LIKE CARBON, NITROGEN, ANDOXYGEN

A. E.. Livingston and H. G. BerryBult. Aim. Phys. Soc. 22, 1321 (1 December 1977)

American Physical Society, San Francisco, California, 23-26 J-anuary 1978

79. CALCULATIONS OF HIGH-ENERGY HEAVY-ION COLLISIONSA. R. Bodmer

Bull. Am. Phys. Soc. 23, 98 (January 1978)

80. CROSS-SECTION MEASUREMENTS FOR THE Li(p, lie)4HeREACTION AT PROTON ENERGIES BETWEEN 0. 1 AND1.0 MeV

A. J. Elwyn, R. E. Holland, C. N. Davids, L. Meyer-Schitzmeister, F. P. Mooring, and W. J. Ray

Bull. Am. Phys. Soc. 23, 97 (January 1978)

256

Publications

APS, San Francisco, January 1978 (Contd.)

81. SIMPLE FEATURES OF THE INTERACTIONS OF PIONS

WITH NUCLEIH. E. Jackson

Bull. Am. Phys. Soc. 23, 1 (January 1978)

82. FUSION CROSS SECTION BEHAVIOR OBSERVED IN 'LIGHT'HEAVY ION REACTIONS

D. G. Kova r

Bull. Am. Phys. Soc. 23, 98 (January 1978)

83. ON THE CONDITIONS REQUIRED FOR THE r PROCESSEric B. Norman

Bull. Am. Phys. Soc. 23, 67 (Janeia ry 1978)

84. ENERGY LEVELS IN 155Sm

R. K. Smith r, K. Schreckenba ch,e A. I. Namenson,W. F. Davidson,' H. G. Borne r, J. A. I-Pinston,

D. D. Warner, T. V. Egidy,* and W. Stofflt

Bull. Am. Phys. Soc. 23, 91 (January 1978)

D. PHYSICS DIVISION REPORT

1. THE SPEAKEASY-3 REFERENCE MANUAL, LEVEL MU, IBMOS/VS VERSION

Stanley Cohen and Steven C. Pieper

Argonne National Laboratory Topical Report ANL-8000

(Rev. 2) (August 1977)

Institute Laue -Langevin, Grenoble, France.

tTechnical University of Munich, Munich, Gerrnany.

257

Staff 259

STAFF MEMBERS OF THE PHYSICS DIVISION

The Physics Division staff for the year ending 31 M;t rch1978 is listed below. Although the members are classified by programs,it must be understood that many of them work in two or more of the areas.

In such cases, the classification indicates only the current primary

interest.

In the period from 1 April 1977 through 31 March 1978,there were 41 temporary staff members and visitors (including 12postdoctoral fellows), 19 graduate students, and 1 1 undergraduates. In

these lists, the Temporary Scientific Staff are those with appointments

for -9 months, while Visitors are on shorter appointments. Research

Participants come to Argonne part-time for research while continuingtheir work at their own institutions.

EX(PEBRIM MENTAL N'JC LEAR PHYSICS

Permanent Scientific Staff

Lowell M. Bollinger, Ph. D. , Cornell University, 1951

CrIy N. Da vids, Ph. D. , California Institute of Technology, 1967

Alexander J. Elwyn, Ph. D. , Washington University, 1956

John R. Erskine, Ph. D., University of Notre Dame, 1960

Gerald T. Garvey, Ph. D., Yale University, 1962

tIn charge of Superconducting Linac Project.

$Full time at Argonne. Also Visiting Scholar at the Enrico FermiInstitute, University of Chicago.

Temporarily at D. O. E. Headquarters, Washington, D. C.(December 1977-August 1979).

'Director of the Physics Division.

260

Walter Henning, Ph. 1). , Technical University, Munich, 1968

Robert E.. Holland, Ph. D. , University of Iowa, 1950

R oy J. Holt, Ph. D. , Yale University, 1972

Harold E. Jackson, Jr., Ph. D., Cornell University, 1959

Teng Lek Khoo, Ph. I). McMaster University, 1972

Dennis G. Kovar, Ph. D., Yale University, 1971

Alexander Langsdorf, Jr., Ph. D., Massachusetts Institute of

Technology, 1937

John J. Livingood, Ph. D. , Princeton University, 1929

Luise Meyer-S(htzmeist(r, Ph. )., Technical University of Berlin,1943

F. P. Mooring, Ph. I). , University of Wisconsin, 1951

John P. Schiffer, Ph. 1). , Yale University, 1954

Kenneth W. Shepard, Ph. D., Stanford University, 1970

Robert K. Srnither, Ph. 1)., Yale University, 1956

Thomas P. Wangler, Ph. D. , University of Wisconsin, 1964

II J. L. Yntema, Ph. D., Free Unive rsity of Amsterdam, 1952

Benjamin Z eidman, Ph. D. , Washington University, 1957

Tlempora ry Scientific Staff

Thomas J. Bowles, Ph. D. , Princeton University, 1977

Donald F. Geesaman, Ph. 1). , State University of New York,Stony Brook, 1976

Ronald M. Laszewski, Ph. D. , University of Illinois, 1975

Catherine Olmer, Ph. 1). , Yale University, 1975

Michael Paul, Ph. D., Hebrew University of Jerusalem, 1973

tRetired May 1977.

Emeritus.

Associate Director of the Physics Division. Joint appointment withthe University of Chicago.

In charge of Tandem accelerator operations.

Staff

Staff

Karl Ernst Rehm, Ph. D., Technical University, Munich, 1973

(From Technical University, Munich)

Stephen J. Sanders, Ph. D., Yale University, 1977

Edward J. Stephenson, Ph. D.., University of Wisconsin, Madison, 1975

Sarnuel L. Tabor, Ph. D., Stanford University, 1972

Visitors

Jc)zsef Cseh, Ph. D., Kossuth University, Debrecen, 1977

(From Hungarian Academy of Sciences)

Francis W. Prosser, Ph. D., University of Kansas, 1955

(From University of Kansas)

*Loyd L. Rutledge, Ph. D. , Texas A & M University, 1974

(Research participant from Northwestern Unive rsity)

Brian B. Sabo, Ph. D., University of Minnesota, 1973

(Resea rch participant from St. Olaf College)

Ralph E. Segel, Ph. D., Johns Hopkins University, 1955

(Resea rch participant from Northwestern University)

Supporting Staff

John J. Bicek

Patric K. Denllartog

Wihiam f. Evans

Joseph 1%. KuLaga

James R. Specht

Robert V. Straz

George E. Thomas, Jr.

James N. Worthington

No longer at Argonne as of 31 March 1978.

tMax Kade Foundation Fellow. Joint appointment with the Enrico FermiInstitute of the University of Chicago.

fTransferred to Applied Mathematics Division, June 1977.

261

262

Graduate Students

Ts ewei Chen (Northwestern Unive rsity)

Ka sra 1)aneshva r (University of Illinois, Chicago Circle Campus)

Alexandrin Davidescu (University of Chicago)

Suzanne A. Gronerneyer (Washington University)

Albert. L. Hanson (University of Michigan)

Robert D. McKeown (Princeton Unive rsity)

Martin J. Murphy (Unive rsity of Chicago)

,ric B. Norrman (University of Chicago)

Krishnaswamy R1aghunath;tn (Northwestern University)

Timothy R. R enner (University of Chicago)

TI I-IOR E;TICAL PHYSICS

Permanent Scientific Staff

Yehuda B. Band, Ph. )., University of Chicago, 1973

Arnold R. Bodrner, Ph. D., Ma rnchester University, 1953

Fritz Coester, Ph. D. , University of Zurich, 1944

Benjamin Day, Ph. D.., Cornell University, 1963

Dieter Kurath, Ph. D. , University of Chicago, 1951t

Robert D. Lawson, Ph. D., Stanford University, 1953

Tsung-Shung Harry Lee, Ph. D., University of Pittsburgh, 1973

Malcolm H. Macfarlane, Ph. D. , University of Rochester, 1959

No longer at Argonne as of 31 March 1978.

Joint appointment with the University of Illinois, Chicago CircleCampus.

Temporarily at Niels Bohr Institute (September 1976-May 1977).

Joint appointment with the University of Chicago. Temporarily atIndiana University (Setpember 1976-June 1977).

Staff

Staff

James E. Nonahan, Ph. D., St. Louis University, 1953

Nlurray Ptshkin, Ph. 1). , Cornell Unive rsity, 1951

St ven C. lPitlper, Ph. 1)., University of Illinois, 1970

J)ht nni Rafelski, Ph. I)., Johann Wolfgang Goethe Univ. rsity, 1973

I'emporary Scit' ntific Staff

Michel Betz, Ph. D., Massachusetts Institute of T'ec hnology,F"M, rry J. Iip)kin, Ph. ID., FPrinceton University, 1950

l"(FromV Weizmn,;irn Institute of Scien ()",,,r-k J. Rho;-d(-s-I1rowtt, Ph. [)., Univc rsity of surrey, 1977

1977

Visit rs

F1ran 'c5(sco Iachello, Ph. 1)., Na ssachusetts Institute of Te chnology, 1969

(From Kernfysiso h Versneller Instit nut , Gr ningen)

Mitsuji Kawai , 1). Sc. , Tokyo University, 1960

(rurn Kvushu University)

KoIniha ru Kuboder a, Ph. 1)., University of Tokyo, 1971(Y rom Univ( rsil v tjf Tokyo)

Aln D. M 1a cKellr, Ph. 1)., 'T'exa s A & M University, 1965(Pesearch participant from University of Kentucky)

Ulrich B. Mosel , Dr. Phil. Nat., Uinive rsity of Frankfurt, 1968(From University of Giesstn)

Wi lliarn 1). Teet rs, Ph. D. , Univc rsity of Iowa, 1968(P (starch pa rticipant from Chicago State University)

George T. Tranrnell, Ph. D., Cornell University, 1950(Resea rch participant from Rice University)

John G. Zabolitzky, Ph. D., Ruhr-Universitt, 1972(From Ruhr-Universitit)

Graduate Students

Soumya Chakravarti (University of Chicago)

Constantine N. Panos (University of Illinois, Chicago Circle Campus)

No longer at Argonne as of 31 March 19/78.

Associate Director of the Physics Division.

tTemporarily at Institut Theorctische Physik des Universitat,Frankfurt (April 1977-May 1978).

Joint appointment with the Fermi National Accelerator Laboratory.

263

Staff

SPEAKEASY CENTER

Permanent Scientific Staff

Stanley Cohen, Ph. D., Cornell University, 1955

Temora.ry Staff

Monika A. Wehrenberg, M. A., School of the Art Institute of Chicago,1972

Graduate Students

Kathryn J. Blackmond (University of Michigan)

Thomas P. Grace (University of Illinois)

Richa rd I). S< hlichting (College of William & Ma ry)

Robert M. Sweiger (St. Olaf College)

EXPERIMENTALL ATOMIC AND MOLECULAR PHYSICS

Permanent Scientific Staff

Joseph Berkowitz, Ph. D. , Harvard University, 1955

tH. Gordon Berry, Ph. D. , University of Wisconsin, 1967

William J. Childs, Ph. D., University of Michigan, 1956

Santosh K. Das, Ph. D., University of California, Berkeley, 1971

John H. D. Eland, D. Phil., Oxford University, 1966t

Donald S. Gemmell, Ph. D., Australian National University, 1960

Leonard S. Goodman, Ph. D., University of Chicago, 1952

Manfred S. Kaminsky, Ph. D., University of Marburg, 1957

Victor E. Krohn, Ph. D., Case Western Reserve University, 1952

No longer at Argonne as of 31 March 1978.

tJoint appointment with the University of Chicago.

*In charge of Dynamitron accelerator operations.

Assistant Director of the Physics Division.

264

Staff

tGilbert J. Perlow, Ph. D., University of Chicago, 1940

G. Roy Ringo, Ph. D., University of Chicago, 1940

Stanley L. Ruby, B. A., Columbia University, 1947

Temporary Scientific Staff

Paul A. Flinn, Sc. D., Massachusetts Institute of Fechnology, 1952

(From Carnegie -Mellon University)

IElliot P. Kanter, Ph. D. , Rutgers Unive rsity, 1977

Siu-Kwong Lam, Ph. D. , College of William & Mary, 1975

A. Eugene Livingston, Ph. D., University of Alberta, 1974

Werner J. Pietsch, Ph.1)., University of Cologne, 1972

Anthony J. Iatkowski, Ph. D., New York University, 1975

Gerhard I. Wortmann, Dr. rer. nat. , Technical University, Munich, 1972(From Technical University, Munich)

Visitors

Patrick J. Cooney, Ph. 1). , State University of New York, Stony Brook,1975

(From Middlebury College)

Thomas W. Dombeck, Ph. D., Northwestern University, 1972(Research participant from University of Maryland)

Bailey L. Donnally, Ph. D., University of Minnesota, 1961(From Lake Forest College)

Ben Greenebaum, Ph. D., Harvard University, 1965(Research p participant from University of Wisconsin-Parkside)

James P, Hannon, Ph. D., Rice University, 1966(Research participant from Rice University)

Jeffrey W. Lynn, Ph. D., Michigan State University, 1972

(Research participant from University of Maryland)

Ove Poulsen, Ph. D. , University of Aarhus, 1976(From University of Aarhus)

Zeev Vager, Ph. D., Weizmann Institute of Science, 1960(From Weizmann Institute of Science)

No longer at Argonne as of 31 March 1978.

tJoint appointment as Editor of the Applied Physics Letters.

265

266

Supporting Staff

Charles H. Batson

John A. Dalman

Peter J. Dusza

Walter J. Ray

Bruce J. Zabransky

Graduate Students

George R. Fenske (University of Illinois)

Gerald S. Gabrielse (University of Chicago)

Robert C. Teitelbaum (Northwestern University)

ADMINISTRATIVE STAFF

tAlbert J. Hatch, M. S., University of Illinois, 1947

No longer at Argonne as of 31 March 1978.

tAssistant Director of the Physics Division.

Staff