B. A. R C.-I012 GOVERNMENT OF INDIA TtHTHJ 3v3ff 3T(4H ...

B. A. R C.-I012

GOVERNMENT OF INDIA

TtHTHJ 3v3ff 3T(4H!

ATOMIC ENERGY COMMISSION

ANNUAL REPORT

OF THE

NUCLEAR PHYSICS DIVISION

Period Ending December 31, 1977

Edited by

C. L. Thaper, N. N. Ajitanand and S. S. Kerakatte

BHABHA ATOMIC RESEARCH CENTRE

BOMBAY, INDIA

1979

. A. R. C . - 1 0 1 2

GOVERNMENT OF INDIAATOMIC ENERGY COMMISSION

uof

ANNUAL REPORT

OF THE

NUCLEAR PHYSICS DIVISION

Period Ending December 31, 1977

Edited by

C. L. Thaper, N. N. Ajitanand and S. S. Kerekatte

BHABHA ATOMIC RESEARCH CENTREBOMBAY, INDIA

1979

-ii-

Keporta previously issuud in this series are as follows:

BrtHI bO1 P e r i o d L n d i n g December 3 1 , 1969

BMHI 557 P e r i o d Lndiny December 3 1 , 1970

BrtRL-633 P e r i o d Lnd iny Oecember 3 1 , 1971

B H H C - 6 9 4 P e r i o d Lnd iny December 3 1 , 1972

BHHL-76B Period Lnding Ltecembur 3 1 , 1973

BHHC-843 Period Lnding Oacembsr 3 1 , 1574

BARC-878 Period Lnding Uucember 3 1 , 1975

BARL-97B Period Coding December 3 1 , 1976

f UHLUKJHU

This report covers the research and development activities

of the Nuclear Physics Division for the calendar yaar 1977. The

Division is organised into thrsa main research sections and a

numbar of supporting service sections. The chart in the report

shows the organisation aet-up including a briar description of

the activity of each suction.

In the beginning of the report of each research section a

brief introduction is included giving tha scope and perspective

for the current research activity. One of the major strength of

the Divisional activities has been the emphasis on the instrumenta-

tion- development- programms . All the major projects have made con-

siderable progress during the year.

The number of papers published in Journals or reported at

national and international conferences are listed at the and of

the report. These i add up to more than 95 which indicatea about

10jb increase in the similar number for the previous year.

The other academic activities which include holding of tha

regular Physics Qolloquia, Participation in teaching and training

activities, active participation in the Annual Nuclear Physics and

Solid State Physics Symposium as well as other national and inter-

national academic societies and committees have been maintained at

the same level as in the previous year.

M.K. MehtaHead, Nuclear Physics D iv is ion .

F oteuiora ili

bllUO STAR

Nautron Scattering

1 . Spin-Tran6fer due to Covalency for the Tet rahedra l - 2Si te Fe 3 + Ions i n Fe304 - V.C. Rakhecha and N.S.iatya Piurthy

2 . f ia jnet ic structure of Cu Pd Plnrtl - S.K. Paranjpa and 3R.J. Begum

3. Polarised Neutron study of Maynetic Moment Q i s t r i - 5butions in Ni i_ xRu x MlloyB - L. dadhaw Rao, R. Cha-k lavar thy , I. J i rak and N . j . ^atya flurthy

4. Ammonium Ion Vibrat ions in nixed Hinmonium— Potassium 7Hdlides - j . K . ainna, B.A. Oasannacharya andC.L. Thapsr

5. Coexisting Phases in NH4I - P.a. Goyal and 8B.A. Oasannacharya

6. Neutron Incoherent Llastic Scattering from NH^I, 9NH^Br, (NH 4) Q K I and (NH 4) n < 1 K Br -P.b. Goyal and B.A. Oasannacharya

7. fleorientational notion of Ammonium Ions i n Octa- 11hsdral tinuironmenta - P. a. uoyal and B.A. Dasa-

a . Phunun studied in oC-KN03(Phaae I i ) - K.H. Rao, 12P.K. Iyenyar, A.H. UunKatesh and P.R. Uijayarayhauan

9 . L a t t i c e Oynaroics of KNu3 - S.L. Chaplot and K.R. Rao 12

1 0 . Clontt) Carlo Calculat ion of the Hot Neutron source 14jpactrum - - . L . Chaplot, P.R. Uijayarayhauan and

l>lurtny

Piossbauer iapectrascopy and Compton scat ter ing

1 1 . Ooubie Resonance Closabauer Spectroscopy - K.R.P.It . 16Hao and N.K. Jaygi

12 . A l t e r a t i o n of Umenita - N.K. Jaygi and K.R.P.M. Hao 17

13. Thermodynamics uf a simple o i ta (Juenched Wayne t i c 1QMixture - N.K. J a y y i and K.R.P.N. Rao

- vi -

14. Compton Prof i le stud/ of Fefll and CoAl - P. Chaddah 19and V. u. julmi

1b. Lffect of Hacttun ourrelatii>ns on the Liectron 19Munumtum Density in Molten Metals - P. Chaddah

16. t-xperimuntaj. itudy of Con|jton Prof i le of Beryllium - 20P. Lhaddah and U.C. jahni

17. Llectron Mumenturo Density in aubst i tut ional ly Ois- 21ordurcri rtlloya - P. Uiaddah

Light Juattorin^ and Liquid crystal studies

tO. Laser Hainan study of thu urder-Qiaorder Transition 22in («H ) Lut l -2H C - A.P. Hoy, I/. L. iahni andn.L. Banadl

19 , Laser Hainan acudy i n the fl ixed (Double) j a l t s 24|(NH4 ) i _ x K x l 21-ULI4 .2H20 - n.L. Bansal andu.L. j dhn i

<;U. Tempuratura Jependdnce uf Ku ta t i una l Cor re la t ion 26funcLion i n Cyciohaxune - I I . L. Bansal and A.P. rtoy

21. Disordwrdd L iqu id C r y s t a l l i n e Phase i n the Compounds, 26p-n-AlkoxyElenzylidane-p-AininoBenzoic Acida - K. UshaUeniz, H.b, Pciranjpe and P.b. Par wathanathan

22. j t r u u t u r a l study of the omectic H Phase of Hx8PA 29(6 0 .3) - K. Ushd Deniz, A . I . Clehta and U.R.K. Rao

Other Topics

23. Res is t i ve i t a t e s i n Superconductors — G. Oharmadurai 31and B.A. Hatnam

2*. ao l id j t a t e Phenamena From the Standpoint of Fun- 31c t i o n a l Analys is - H. iubramanian and K.U. Bhaywat

2b. A simple Proof of li/icjner's Theorem - fl. Jufaramanian 32and K.U. Bhaguat

26. extension uf Induced Monomial Representation Theory 32to jemi-LUrect Product Groups - I.V.V. Rayhauacharyulu

27. U'inecalized lionomial Representations and Their Appl i - 33catiuns - I.\i.\l. Hayhauacharyulu

— V I I. —

FIJ-.IUN PHYalCS 35

1. flultiparamuter studies of Fragment hays, Lnergy and 36Angle Correlations in Long Range Alpha ParticleAcoomjjaniud fission of oby induced by ThermalNeutrons - ri.K, i-houdhury, 0.1*1. Nadkarni, P.N. RamaRao and b. o. Kapoor

2. Multiplicity LfistriLiution of Prompt Gamma Hays in 39opontanuous Ternary Fission of 2^2Cf - R.K. Choudhury,J.L. Plohanakrishna and tf.5. Ramamurthy

j. Quantitative Hesolution af 2^4 Th Anomaly - n. Prakash 40and h.-j. Hhandarx

4. Analysis uf Frajmont Anyular Jistributions in Fisa— 42ion Induced by Heavy Iuna - Ht-kha Gouil, H.K. Chou-dhury and J.J. Kapoor

5. Transmission Throuyh Riharmonic Usciilatur Potyn- 43tidla: Mpplicatian to Double-Humped FissionBarrier - 1*1. Prakash

6. TFJO Hesponsti to Fragments from Light Lharyed 44Particle Accompanied Fission of ?3°U - N.N, Ajit-anand, K.N. Iyenyar and j.rt.o. Ciurthy

7. emission of tneryetic Liyht Charged Particle 46(Z = 1,2) in Fast Neutron Fission of 2;35U -0.1*1. Madkarni, K.K. Choudhury, o. b. Kapoor,6. Krishnarajulu and G.K. fflehta

PHYblLS

1 . Real and Imaginary Parts of the Nucleus-Nucleus 50In terac t ion ut>ing a Microscopic Approach -b.K. Gupta and S. Kailas

2. Volume In teyra ls of Wucleon-Nucleus Optical Puten- 50t i a l s - b. Kailas and S.K. Gupta

3. Comparison of Nucleon acat ter iny t.ross ^actions 51wi th thu JLM Microscopic Optical Model - S. Kailasand J . K . Gupta

4 . F luctuat ion Analysis of Ca(p,n) be Total Exc i ta- 52t i on Function from 1.9 to 5.1 fieU - Gulzar Sinyh,S. Ka i ias , A. Chatterjoe, S. ba in i , M. Balakrishnanand Pl.K. Mahta

- u i i

b. La lcu la t ion of (n , 2n) Lross Sections Around 5214.5 MBU uainy an Inteyratud Preeu,uilibr ium-cum-S t d t i s t i c a l Model - rt.. Chatter jae and S.K. liupta

446. Resonance Spectroscopy of bha Nucleus Ti - 53

•. Lhat tur jue , i . Sa in i , S. Ka i las , 1*1. Balakriahnanand Pl.K. Fluhta

7 . Nuclear structure of Scandium Isotopes - b. Saini 54and Pl.R. Gunye

8. Direct and Lo l lec t ive Nucleon-Capture, uainy 58Microscopic Opt ical Potent ia l - D.H. Chakrabartyand S.K. Gupta

9 . 1 9 F(<* . ,n ) 2 2 Na RBaction - f l . Balakr ishnan, 5. Kailaa 60and fl.K. Mehta

1 0 . Level Scheme of 8 Kr - Y.K. Mgarual, C.l/.K. Paba, 61S.n. bhara th i , U.fl. Qatar, H.C. Jain and B. Lai

1 1 . Search fcr Bound Pol/neutron Nuclei in the Fiaaion 61of 236u _ c.VvK. Baba, \l.n. Qatar, V.K. Bhargaua,fi.H. I y e r , S.G. Itarathe and U.K. Mao

12 . A. method of Al ternate Recording of ON und OFF 63Resonance ^ - S p e c t r a at a Fast Rate - D.R. Cha-krabar ty , H.H. Oza and N.L. Ragoouansi

13 . Strong Absorption Plodel for Pion Induced Knock-Out 65Reactions - 8.K. Jain and S.C. Phatak

•+ + 1?14. Off Shel l t f f e c t s i n ( IT , IT P) Reaction on C - 66

S.C. Phatak and B.K. Jain15. Scrutiny of the Impulse Approximation for ( p , 2 p ) 69

Reaction - B.K. Jain

16. Nuclear F r i c t i o n and the Imayinary Part of the 71Nucleus-Nucleus In te rac t ion Poten t ia l -Bikash Sinha

17. Aueraye Nucleon-tneryy Lxc i ta t ion and Lneryy 71Dissipat ion i n Heauy-Ion Co l l i s ion - S.C. Phatakand Bikash Sinha

13. The Imayinary Part of the Nucleus-Nucleus Optical 1\Potential - S.C. Phatak and Bikash Sinha

19. The Nuclnus-Nucleus Interaction Potential using 72Oensity-Oepandent Qelta Interaction - BikashSinha arid S.A. l*loszkowski

20. Nuclear Utructure Calculation? using Momentum- 72Ddpdndent Delta In teract ions (MOO) - Bikaahbinha and jtuvan * • Noszkoiuski

2 1 . Microscopic Calculat ion of 0-ot Scatter ing with 736-Body Antisymmetrized Wai/e Function - Kir anKumar and A.K. Jain

22 . Nuclear exchange as a Hchanism for strongly 77Damped Heavy Ion Col l is ions — A.K. Jain andN. Sarma

2 J . t m p i r i c a l Rules for b u b s t i t u t i o n a l i t y in P.ita- 80stable burface Alloys Produced by Ion Implan-t a t i o n - O.K. bood

24. Ion Implanted Surface Alloys in Nickel - 81O.K. Suod and G. Otsarnaley

25. B l i s t e r i n g by Helium Ion Bombardment - D.K. ~>ood, 81f). bunder Hainan and R. Krishnan

LXPLHIflLMTAL TLLHUIqULb AM) INSTRUfOTrtT ION

1 . Isotope Separator Section - I/.A. Hat tangadi , 83F.H. Bhatnena, K.L. Pate l and L. ahallom

2 . TandBm Accelerator - Pl.G. B a t i g e r i , : . P . Dauid, 84P. Singh, J .N . Soni, C.I / . Rayarappan and U.K. Itehta

3 . Ion Implantat ion - P.K. Bhattacharya, U.S. Bhat ia , 86Pl.J. Kansara, A.G. liiagh and N. Sarr.a

4 . I/an de Graaff Uperations Section - U.A. Hat tangadi , 89S.N. Plisra, O.S. Bisht , S.G. Shukla, n.£. Doctor,S . J . Mandke, P.R.S. Rao, G.V. y h a t t , R.P. Ku lkarn i .R.I / . Patkar and N. Fernandas

5 . Mon-Oestructiue Estimation of Boron i n Aluminium - 92Y.D. Dande and N.C. Jain

6 . Converter Screens for Neutron Radiography - 93Y.D. Oande and S.R. Chinchanikar

7. Nuclear Radiat ion Detectors 93a) BF3 and He-3 Detectors - R>S. Udyawar and

G.U. Shenoy

b) Soft X-ray Detectors for ftossbauerSpectrometry - G.U. Shenoy

c) Position Sensitive Detectors - Y.O. Oandeand G. U. Shenoy

S. Laser Plasma Tubas - S.R. Chinchanikar and 94M.L. Bansal

9. Lou Lneryy X—ray Tube for Energy Qisparsive 94X-ray Fluorescence Analysis — b.K. Kataria

10. X-ray Fluorescence Analysis of Plateriala - 96S.3. Kapuor

a) Analysis of Hare Larth ' i ipur i t iea i n Thoria 96Fuel - N. La i , j . K . Kat. ia and K.U. Ui6hu»a-nathan

b) Analysis of Alloys - Fl. Lai g ?

c) Trace element Analysis of Ligarette Tobacco - gyl"l. La i , B. i/.N. Hao and J . K . Katar ia

d) Analysis of Minerals from Geological Surt/ey yyof India (GSI) - -^.K. Katar ia, Rakha Gov/il ,K.l/. l/ishwdnathao and H.K. Choudhury

e) Analysis of Pl/C Tubings - K.I/. Vishwana'than 97and Hefc.'::: Goi/il

f) ts t imat ion of Liallium in Bayer Liquid - ggK.I/, i/ishwanathan, J . K . Kataria and R. Gov/il

y ) Analysis of Trace Amounts of Lead i n Soil ggbamples - 1*1. Lai and K.U. Uishuanathan

1 1 . Loin Temperature Laboratory

a) Heliu.-i L iqu i f io r and Associated Work - ggN . J . Liatya Flurthy, l/.K. Lhopra, G. Oharma-du ra i , T. tir iniuasan and A.P. Bayool

b) Superconducting Magnets - N.a. Satya Clurthy, 99U.K. Chopra, G. Oharmadurai, T. Sriniuasanand A.P. Bayool

c) Dilution Refrigerator - U.K. Lhopra •) QQ

12. A Lold-Neutron Source for CIRUti - S.K. Sinha, 1 QQC.L. Thaper and B.H. Oasannacharya

CHART 1 0 3

PUfciLILMTIUNS AhQ PMPLRJ 1 07

UTHLR 'jLl^NTlFli. ^uTIUITlLa 1 1 g

SOLID STATE PHYSICS

-1-

SCILIO STATS. PHYSICS

The Solid State research activities have continued to be

centered around neutron scattering at the CIRUS Reactor but the

fact that it will be a feu years before a new source becomes

available has been taken note of in new programmes. Thus most

of the new inputs have been in other techniques like light

scattering, Compton Scattering and flo'ssbauer Spectroscopy. The

development of cryogenics has also been given high priority in

view of its almost inevitable need in all modern solid state

experimentation. This phasing of emphasis will be readjusted

when the criticality of R-5 approaches. Meanwhile whatever

neutron instrumentation is being newly built for ongoing

programmes at CIRUS has been designed with eventual use at

R-5 in mind.

- 2 -

I Nautron tcattarinq

1 . Spin-Tranafur dud tu LaudUncy fpr the TetrJhudral-Slte Fe f

Ions in Fe 0 (V.U. Kakhtcha and N.b. Satya PiurthyTJ

Neutron mtmsurem;,nt6 on natural ^U,U crystals had giuen

evidence for a siynificantly ldrye cuvaluncy for thB Fe iona

on tutruhejral (A) sites . The.>e conclusions nave buan verif ied

from further unpularised >Jnd polarised nautron measure nents on a

8toichiornetric 3ynthetic crystcil of Te 0 ' ' . Nearly identical- j ^

magnetic structure amplitudes for the A-stte-only rafloctio/is, aa

in the natural crystal , were obtained. A detailed comparison of

tht A-sitt' from factor waa also made with the Fe tetrahedral form

factor in a closely related compound Yttrium Iron Gamut (VIG). In

thu l-3ttar co.ii|jound the di£>t<ancu betuaen an Fe (tetrahedraJ ) Ion

and th« nearest oxyyone is nearly tho same as in Fe,0 . As axoected

u fa ir agreement uss found bntuiaen the two.

A quantitative avaluation of A-site coualency has bean made

uainj a molecular orbital theoretical description for the magnetic

electron wave functions for tht cluster (FeO ) . The 3d orbitals3+ —2

of FB and 2p orbitals of 0 were considered in this traatm^nt4 )

which follows tha original formulation due to Hubbard and flarshall .

Tha ^pin density arising from the e and t^ orbitals was resolved into

sphtrical harmonic components and the component Form 'actor* (spherical

and asphurical) were evaluated. These form factors .^re incorporated

in a ltast-aquurea comparison of the calculated and exparirnantal

maynetic structure amplitudes. I t was established from tha analysis

that about 28,4 of the 'ionic' spin daneity is ttsnsferred away from

the central FB i a n to tha four neighbouring oxygens. The cf- coua-

lency was seun to predominate!. The three coualency parameters inuolvsd

in the theory uars evaluated

The lack of cantre of inversion for the tetrahedral site results

- 3 -

in i ts magnetic form factor haviny an iroayinary part disci. The

lattur is albo obtiiirted in the aboui analysis. I t has been shown

that the imaginary part of A-site form factor does not contribute

to the A-site-only reflections but does so to the other reflections

in an important way.

1) \I.C. RakhechH, H« Lhakrauarthy and N.S. Satya Plurthy, 3. da.Phya. 38., C1-10? (1977).

2) l/.C. Rakhecha and N.S. Satya Clurthy (to be published).3) U.C. Rakhecha, Ph.D. thesia (1977), Uniw. of Bombay.4 ) 0. Hubbard and W. flarshall, Proc. Phys. Soc. B£, 561 (1965).

2. naqnetic Structure of Cu Pd PinAl (S.K. Paranjpe and R.J. Becjum)

* neutron diffraction experiment has been done on mixed Heualer

alloy (Cu I'd) Mnfll as part of a study of the series Cu, Pd UnAl,

uho3F> end merohsrs are ferro- and antifBrrom.ignatic reipectiwoly for

x = 0.0 and x - ^ .0 , to ste the effect of A and C-sits atoms on the

magnetic ordsrini) in Hwutsler al loya. 5o far moBt of the reported

studies have beuri done on the role of B and Q-aite atoms.

The polycryntalline sample of Cu Pd PlnAl was prepared using

4N-purity constituents and melti.ny in an R.F. furnace under vacuum.

The bulk was than powdered and annealed in vacuum at 600 C. The X-ray

dif fract ion pattern usiny Cu-K^ line and neutron di f f ract ion pattern

shoumd a dinyle phase alloy with c e l l dimension of 6.008 + 0.005 A.

The neutron diffraction patterns taken at 300K and 140K are shown

in Fig.2. The intensities of reflections with h+k+1 m 2n + 1 are lou

uhich suggest Pln-Al disorder. At loii tamperature the intensities of

these reflections increase whereas those of even reflections remain

practically unaffected. This indicates the magnetic nature of

h+k+1 • odd type reflections. Mo change in the intensities* of (111)

and (200) reflections was found, when a magnetic f ie ld of »--> 4k0e was

applied para l le l to tha scattering vectors at 140K, proving the absence

of any ferromagnetic component to these ref lections. Thus the basic

-4-

magnetic structure is antiferrumaynetic. Tho Nael temperature was

200

100in

I

100

OBSERVED AND CALCULATED PROFLE

» .l.ill• OBSERVED

CALCUlATf B

U0K

300 K

• • ' -V,.

20 2» 30 35 40

l i y . i Observed and caluulated profilbs fur C

found to bo 363 K from the temperature dependence of (111) ref lect-

ions. Inure uas no rhan-.ji in tha intensitiea of (200) and (220)

rt f lact ions canfirmini; Mn-Al disorder. The structural parameters

hai/e been obtainiid using profi le refinement technique. Tig.2 ahouis

•.„-'! a f i t tad curve for 140 K dif fract ion pattern. The magnetic

ri.jinents per1 fin atom haje been found to be 2.6 + 0.2 /*- and

3.8 +B

at 300K and 140K respectively.

Thd part ial rBplacBroant of Pd by Cu in Pd-dnAl has raised the

Neei temperature from 240K to 363K without affecting the chemical

structure. Thi9 indicates the important role of A and C-aita •toms

on the magnetic orderiny of Heusler al loys. The quantitativa infor-

mation on magnetic interactions in this aystem is expected from the

study of the entile series. Theso studies are in progress.

- 5 -

i. Pul-.ifii.uci Njutiur> ~t.udy uf Hdjm.ti<- JVi'/u=nl Uis t r i ' ut i unsi"_JJi. 'if A j 1 u y a ^L. Hiidfuv Hun, H. Lh Jkr-i v.irthy., I . Jir-)k*..fid h.ii- LLityu I'lurl.hy)

Un the pol.ir ISMCI neutron bpuctr unn; ter, thu aajurBmunts of

t.hi f u l l thru.-- diintnaional magnetic structure amplitude" in

Ni Hu fainylt/ crystal alloys ware completed for two concentrj-

tions viz. x e 0.0i7 dnd 0.033. (Thuse concentratiuns were quan-

t i t .Jt iut i iy OJtimutBd by X—ray fluorescence and were found to be In

•jLturii with the saturation raagnetlzatiun values measured on these

s*amp 11>a ). In the dBtailed leabt-3L|uareb analysis of the data, tho

I'rtSLnte of Type 1 sucundyry extinction in both thu crystal compo-

sitions was fu l l y accounted for . The 2.7/o alloy was found to

f,ufri=r from yreater extinction (g = 1360 +.71) than the 3.3;a alloy

([j = 24ti + 21). The extinction corracted experimental tiaynatic

utructuro amplitudes uure interpreted in the framawurk of the

Jifii i r superposition model to obtain tho local moments on the

hust (nickel) and impurity (rothenium) sites and tlw aaphcricity

I- iramr-.ttr of the haat moment d is t r ibut ion. Moment density d i s t r i -

f.'otion map;, in various planes of the unit c e l l were obtained by

Fourier inversion. Moment.density maps of the faces of the

Wlyn^-r-Seitz cu l l Showed largo itilunds of positive diffuse moment

dbnsity alony ui th small island of neyativa diffusu moment d'..'nsi ty

in the case of the 2.7/5 alloy (Fiy.3a) while d similar map for

tho 'i.3/l alloy (Fiy.3b) showed a uniform positive diffusu moment

dt-nEity. This; is in sharp contrast to the si tuat ion in pure

nickLl where a uniform neyativ/t diffuse moment density was found

t-.y Hook. Another interesting feature of those studies is that tht;

Hu moment is found to be negative and suffers a drastic change in

magnitude over a small concentration ranye.

-6-

ATOM MOM

Ik)Fly.3 Mument density maps in Ni1 Ru for (a ) x = 2.

(b) x = 3.3#. * *

The- principal results uf the analysis are summarised in Table

TablB 3.1

Bulk Localmoment momunt

0.58 K.

N1U.9-3HuU.O27

Diffuse A3phericitymoment paramet or

-0.0.9/* 0.19

0.16

Ni0.967 "0.U33

+0.06K, 0.18D

•Guest BciBntiut from the Institute of Solid Statu Physics,Prague, Lzachoslovakia.

4 f Ion L ib ra t iona in I*I1XBCI rtmmonluni-Pot833iuni HalldeBi i inha, B. * . Dauannacharya and C.L. Fhapsr )

In elastic scattering uxparimentu ware performed on

Vu . 1 6K U.84 B r ' (NH4>U.3BKU.65

Br' N H 4 B r ' <NH4 >0.16*0.84 1 8 n d

NH I at 1GOK on thfe f i l t e r detector spectrometer. After these4

muaauremante were completed we found that measurements on

W9tiardener at ai

40.04S%.955Our spectra are ahoun in Fly.4. We find

u

%

s *•

I"ry

* J O

*.o

2.0OJ)

T.WOKO.90"

ENERGY TRANSFER (In ctrf1)

Fig.3 N&utron inelastac spuctra for pure and mixed ammoniumhaiides at 100 K.

"localised" translational modes and torsional modes in the mixedsalts ' ' . in pure salts, at the came temperature, much narrower( ^ resolution) torsional peak with hiyher integrated intensity is

observed at a hiyher frequency* Pure NH -halides hava a CsCl st ru-4

cture whereas the mixed salts have a NaCl structure, w ich giuea theNH, ion six nearest neighbours and an octahedral surrounding. In the

NaCl-btructured mixed crystals the width of tha torsional 11ns is

- 8 -

rnucfi broader than the resolution and i t remains broader even at

4.2K. t-uan in the di lute mixture of Gardner et al a similar width

was Found at 80Kf the width is typical of • tetrahedron l ibret ing in

an octahedrul environment. The peak posit ion* uhow only a email

variation with concentration.

1) *.B. Gardner, T.C. tfaddington and 3. Tomkirif.on, 3. Chain. Soc.,Faruday Trans IX, 73., 1191 (1977).

2) H.G. Smith and N. Wakabayashi, Inelastic Neutron Scattering(I.A.I. .A., Uiunna) p.103 (1972).

5« Coexisting Phases in HH 1 (P.S. Goyal and B.A. Dasannacharya)

• recent maynatic relaxation study of bharp and Pintar has

suyyauted that under certain conditions of cooling/heating, the hiyh

temperdture NaLi phase of ammonium iodide can coexist with the lower

temperature phastss ( t ransi t ion temperature = 256K), Ue have carried

out neutron di f f ract ion experiment* on this salt at 3u'O, 240 dnd 220K

using a t r ip le-axis spectrometur with a fixed-elastic-window. Thuja

giv'e direct evidence of tha coaxistencs of the NaCl phaaa with the

low tempuratura phases at ^40 and 22uK respuctiualy. Tho concentration

of Natl phase at 240 and 22UK ha= bean found to be 61# and 2S% res-

pectively, for our experimental conditions.

In view of the ptasent resul ts, we have reinterpreted our earl ier2)

data Mhtire wa had studied nuutron quasielaatic scattering from NH. I

at several temperatures bt/twefen 213 and 3D0K. from these experimanta,

we find that NaCl phase of Nh I can supercool to 243K. The sample

transforms to tetragonal phase at 213K. In the heating cycle, sample

exists in the CsCl phase at 243K, in the mixed phasu betueen 253 and

278K and in the pura NaCl phase above 278K. The concentrations of

NaCl phase at 253, 259, 268 and 278K have been found to be 17.9, 22.4,

30.6 and 37,9 jt respectively. The coexistence af phases cal ls for

grbat care in interpreting any data on Wl I in the temperature ragion

uf the present experimants.

- 9 -

Oatu on neutron quasielciutic scat ter ing expariments in the mixed

phat.1: (2b3-i7tfk) of NH I ha'ja been analysed to obtain the roorientat iorv

timu - f : fur NH + ioru in CsCl phase of NH I . The values of "C at4 4

W3, 2h2, ^b9, 268 and 27UK have butn obtained to be 58 + 5, 47.5 + 7,

JU + 4 , 25 + 4 cind 2U + 4 pSec r Bbpuctively. Thusa rusu i ta Suggest

that tha . ic t iua t ion energy fo r NH ion reoi ian ta t ion in the CsCl phase4

of NH I id of the saint ardor ( *"-» 3 Kcal/mole ) as that in CsCl phasBS4 1 )

of NH Cl and NH Br .4 4

1) rt.R. Sf arp and CI.Cl. Pintar , Uhem.Phya. 25_, 431 (1976).2) P.b. Goyalt B.A. Dasannacharya, C.L. Thaper and G. Uenkataraman,

B..H.R.L. -07U, Annuai Roport of the Nuclear Physics Div is ion(1975) p.74.

Mautron Incohursnt Elastic Scattering from NH.It NH,Br»(NH ) , K .1 and (NH. )_ ,.K., Br (P = j.GoyaJ and

Tha angular var ia t ion of nuutror, incDheront ' e l a s t i c ' scat tar ing

fro^. I)H I , NH Br and (NH, ) •sc.^n -w r a^ room temparature and from

(NH/ )r, <«:Kr n / 1 a t 1 4 0 a n d 3 U t i K h a u e b 8 e n studied u^ing a f i x e d -4 u • i o U « 64

elastic-uindoiu for the scattered neutrons. The measurements were made

usiny a tr iple-axis spec t rombt er (E = 13.78 and t^Z = 1.30 met/ as

achiaved using pyrolytic graphite monochromator/fliter/analyser Combi-

nation). The measured distributions are shown in Tig.6. For N!' Br,

thu present distribution agreea with poor resolution (AC = 12.G meV)

data of Uenkataraman et al ' (shoun by crosses) and for NH.I i t is

consistently lower than the poor resolution data (not shown in the

f igure). The following remarks can be made from the above data:

Thu steeper f a l l of intensity for salts in NaCl phase (NH.I and

the mixed salts) as compared to NH Br, which is in CsCl phase, shows4 +

that reorientation time T for NH ion is smaller in the NaCl phase.4

Houever, as the intensity patterns for a l l the three salts in NaCl

phasa are vary similar, the reorientation times and geometries for

- 1 0 -

NH + ionB in thusu salty are nxpuctuij to be similar.4

Fig.6 Pleasured .inoohurent elaatic scattering from purea n d i n i x u d uitniiunium = > i i l t J .

results for NH Br at room temperature shows that in this salt

The fact that good and poor resolution measurements giv/e similar

is

larger than the time determined by the better resolution experiments

( T =i- 2-^/&F = 6' 5 PS£:c- )• On the other hand, the large differ-

ences betuisBn good and poor resolution measurements for NH. I shows

that in NaCl phase T 4 T o •

2) +If one assumes octahedral jump model ' for NH ion reorienta-

tions, a comparison of the experimental and the calculated (solid

lines in figure) diat'ibutions giues ^ 5 psec in the NaCl phase

of NH I and the mixe,1 salts. Further, a detailed calculation shows

that the present data rules out threa fold uniaxial rotation of

NH *" ion in thase Salts.

1 ) (i. Uunkataraman, K. U3ha U6niz , P.K. I y a n g a r , A.P . Roy andP.R. Vi j a y a r a g h a u a n , 3 . Phys .Cham. S o l i d s 22., 1103 ( 1 9 6 6 ) .

2) R. atock/neyer and H. St i l ler , Phya.5tat. SDI. £7 (196B).

- 1 1 -

V. rt,_,/i'it,n_t_<iti.unal j[2pti._orj of_^nMia_nium Ions in OctahHdral Environ-ments (P.b. kcjyal and B.H. Ja= annacharya )

Nuutron qudbieJait ic scot tur i ry from HiaCl phast; of Nil. I ,

( N H Ju .16 K 0 .84 I a n d ( N H4 )0.16K0.84B r U " l n Q r o t a t i n « " y a t a l spectra-muter, RCS, (E = 4.7B meV, / \E >--. 0.35 HIBU) was reported ear l ia r .

intajuramentfc havu now b-son carr ied out using a t r i p l e axis

, TrtS, (E = 13.78 mal/J, k E = 1.3 msl/) whose accasslbla

moinontum transfBr ( "fcQ. J ranyo is large comparad to that of RC5.

For NH I , thu nisasurumunts hav/s buen carr ied out at room tempuraturs

in the M range of 1.J4 to '3.2k K .. Thu measurements for

' N H 4 ^ ' 1fiKu b4 I a t f O U r t u l" f J u r i j t t j r B d batiuaen 9Q and 300K and for(N" ) -K u / ^ r a t room temperature uere irada for U = 2.89 A . The;lufj_>i.ijlastic scat ter ing data obtained u i ing RL and TAb havs beenanaiysud to obtain NH ion form fac tor , reoriar, at ion rates and i n f o r -mation reyarding rucr ien ta t iona l oa r r i e r . Th" reu j l tB Df prdsonti r ivuut iyat ions aru summarised beinu:

Rourieritst -on timus aru aimi iar for pure and the mixed iodide et

room tumperature ( X ^~> 2.0 ^ 1 . 0 psec). t is somewhat larcjar

fur the mixed bramida. Both for the bromides and thu iodides NH i j n

rt iur iants much faster in NaCl phase than in the CsCl phase.

The v/ariation uf X. wi th temperature i s very small between 98

and 3UUK. Euan a lou hinddriny po ten t i a l , for example \l = 300 cal/mole,

yiwcis a t varying by a factor of three between 100 and 3P0K. Such

a change hao not been obsBrued. This suggests that NH iDi) exper i -

encos a very low barr ie r for i t s ro ta t iona l motion.

2) +A number of rbor ientat iona1 models for NH. ion have been con~

4

sidered. The present form factor studies rule out free rotation,

uniaxial diffusion, uniaxial three fold jumps and 120° jump models.

Hotational diffusion model can bs ruled out using neutron diffraction

data ' . Both the^s data are consistent with a model which assumes

octahedral jumps of NH ion. Howevar, for a four fold rotation

involved in this model, a barrier of 3CJJ cal/mole gives librational

- 1 2 -

4 )

frequencies which are much smaller than the experimentally measured

values of 185 and 233 cm Tor mixed bromide and mixed iodide samples

respectively. To obviate this d i f f i c u l t y , we proposB a model uhich

assumed that a hydro&en atom, say H. , performs rotat ional di f fusion on

a c i rc le purpyndicular Co tha [100^) direct ion . ut f l i p s by 19° -16'

uhonouer a H-N-H plJne overlaps* ui th a (100) pl-ine if the c rys ta l .

Fha modnurad libr<ition<*l frequoncitis mould now givu barriers of '-• '. 1U

end »-» 70 cal/mole fo.r bromide and ic^idtj sample respectively.

1) P.Li. Guyal and 0.* . L)aoanriach<Jr ya , BARC -978 t Annual Report ofthu Nucluar PhysiciJ Uiu i i ion (1976; p.100.

2) H.b. iyymour and A.til. Pryor, Acta Cryst. 26B. 1487 (1970).3) lil. PrBai, Mcta Lry^t. 2a*., 257 (1973).4) b.K. j inha, E.*. Uasannacharya and C.L. Thaper, a r t i c le 4 of

th is report.

3. Phunon btudiafa in caC -KMO (Phase I I ) (K.R. Rao, P.K. lyanyar,rt.M. 1/onKatt.sh and P.ft. i/I jdyar )

Lontinuiny thti work rbport td vdtliuv , mfiasuremunts of dispersion

ru la t icn of phunons by coherent i n t l as t i c neutron scattering tachniques

act; completed aloni, ^ , ( ^ » U, U), £^( G ^ , 0) and ' ( u , 0 / ^ )

directions in o(.*"KNO . The low lying transuerst anj longitudinal3

acuuetic branches «nd a few optic branches are thereby known ncui.

1 ) Dee K.H. Rao, P.K. Iytsnyur, H.H. Uenkatesh and P.R. UiJayarayhawan,B»*HC - 978 , ftnnual Report of the Nuclear Physics Division(1976), p .99.

9. Lattice Dynamics of KNO (S.L. Chaplot and X.R. Rao)

A r i g i d molecular-ion model of KNO., is davaloped makinq uso of1 )

the external mode formalism . Using . jotent ial parameters baaed on

s t ruc tu ra l -s tab i l i t y considerations, the dynamical problem is numeri-

cal ly solved to obtain l a t t i ce frequencies in dL. t £> ar ld V phases

of KNO . Wu have used group theoret ical techniques to obtain tha

frequencies labelled representat ion by representation and to simplify

the numerical problem.

-13-

Fiy.'J sho«6 the dispur:>iun relation in the three phases along

hiyh tiymintilry dir -.ct i uns. Thf.1 nuutr on results of ot -phases ' are

Fiy.9 Lalculated phonandiiipersion curvesin & , ft and Vphases of KN03

along symmetrydirections.

in good agreement with the calculated frequencies. In the fi> and

Y" phases no experimental data (apart from Raman Spectra) exist in

literature Tor comparison*

1) G. l/enkataraman and U.C. Sahni Rex/. Clod. Phys. £0, 409 (1970).2) K.R. Rao, P.K. Iyenyar, A.H. 1/enkatesh and P.R. Vi jayardghauan,

article B of this rtport.

10. Honta Carlo Calculation uf the Hot Neutron bourca SpectrumI"s.L. ChapJLot, P.R. Wijayaraghauan and N.S. Satya T^

In continuation uf the work reported earlier • simple Plonte

Carlo calculation 1J carried out for the neutron gain from the

protutypb hot noutrun suuce fur the LlRUb reactor. The method incor-

porates the cylindrical yuomntry of the hot 6ource moderator in a

radical beam hola< The double differential scattering crosj-«ectlon

far tht yraphite modfcrJtor i« approximated by that of a munoatomic

gas of the same atonic msss and density. Ten Montu Carlo experiments4

each cunsistiny uf 10 nuutron histories were carried out for a hot

source moderator of diamat&r 16 cm end length 16 cm at a tumpsrature

of 154QK, calculated on tho basis of the available nuclear heating2 )

and the characteristics of the specific design . The modlfiad neutron

spectrum, obtained from the Monte Carlo experiments, ia shown in Tig.10

along with the original «(.<cfcrum. . The resulting gain in tha neutron

spectrum is alba shown in tha seme figure. The maximum gain is founda

tu be 7.4 at a neutron wavelength of U.52 A. The error bars shown on

the hot source spectrum and the gain curves indicate the estimated

standard deviations. Typical accuracies of the order of 10% are

obtained near the peaks of the curve***

details of the Monte Carlo method as applied to tha hot source

problem would tie described ole&where ',

- 1 5 -

.5 t 2 3 5 10NEUTRON WAVELENGTH(X)

F i9. l l ) Hot nsutron spuetrum from lionte Larlo c . i lcu ldt ions.

1) b.L. Lhdplat, P.K. IJi jJyarayhdvan and N.b. Jatya Murthy,B«RL - 978 f Annual Heport of thd Nucludr Phyt ic j Diuis ion

(1976) H-145.2) S.L. l ihaniot, P.R. Uijayarayhavan and N.b. batya Mutthy,

SnKC Hd|jort (1976) To-be publi^hfcd.3) Si.L. Chaplot, BHfti. fldport I197o) To be publ ished.

-16-

I I . flosiiijaucr !Jpuct roscopy cind Cownton Scattering

11. Doublb Hbiaorianuo Mo'ssbuuar 5pec tr<jscopy_ (K.R.P.F). Rao andN.K. i

Ooublu R&sunanca Mussbauer Spectrascopy (ORLHOS) is a useful

i^ue tu study relaxation procesbcb, to measure Rayleiyh

scattering ctoi.s sections and tu decipher complicated spuctra to

mention come of i t s tipplicdti ona. Ir, DHEPIGS gamma rays frum a

siiiyit! l inu MaE.ebautr Bourco mountac', an a constant velocity driva

(CUOJ aru jcJtterod frum a bulk s&mpla at a scattering anylt- of

about 9U°. Tha scattered beam i j eneryy analyBed by counting aftar

Ibt t iny i t pasa through a thin sinyld l ine fluasbauer absorber

mounted on a con:'t3nt accrflaration drive (CAD) coupled to a mul t i -

channel analyuer (PICA) and syncronized uith the CUD* A uiidu uiindow

propor Clanal counter i« ;ut'd for getting suff icient intensi ty. Tha

(.1/0 ii- adjusted to move the source in such a way as tu match i t s

cin&rgy uith one of tha allowed transitions in tha sample nuclei.

This sultctiwaly populates nnu of tha excited nuclear lev/els in the

scatterur i .o . the sample. The vulocity spectrum of ths scattered

beani obtained by moving the absorber (CAD) in an appropriate rungy

of voloci t ius, uith a fixed source velocity, constitutBs the double

resonance spectrum. A Uouble RLsonancb riOasuauar spectronster W«J

dQBigned, faurlcatcd and tested by recording doubla resonance spectra

of bulk stainless steels. M tenema t ic block diagram of the spectro-

meter is tihuwn In f~is.11.

- 1 7 -

FUNCTIONGENERATOR

TRIGGERI;

X(VELOCITY)

t uCOUNTING

ELECTRONICS mnilY i (COUNTS) " j

MCA

t

tvof

_ 5_~aGRADEDSHIELO

t'. A .O/7 ]i \~TsEC.

*NALVSER

(SCATTERER)

SEC.

BLOCK DIAGRAM OF OREMOS

Fiy.11 A suhumatii, bluuk oiayrum of JHEITOS.

12. rti.tBrat_iori of Ilirmnite (N.K. Jayqi and K.R.P.P1. RJO)

Ilmunita ifeTiCi, ; uniieryoua a l t e r a t i o n to r u t i l e (TiO ) umiur

a m b i e n t c o n d i t i o n a . Ju t tn thd rtCfcnt i n t e r t n t in c;jnu-.3i' t . inq f r e f i iy

a u t i i l u h i u i im, n i l t tu t n i ra i<i t i u u l y r.iT£; r u t i l f , H s t u d y of t h i s

ax t<.r<ii.iun mad unc3oTtdk«n. uur (juiudtsr x—ray dif ' f r . i c t i o n dnd

l iub tbdu^ r d a t a , t u k u n d t roumF l i g . N . k li.Lj.He t c m ^ u r d t u r u s l a a d t o

t h e fu

Truifi. aid two

Ljsi^r I. o cuni jlKtb

o FtTiU

of a l t e r a t i o n of .uhich the f i r s t onti i s

Ti U,

C i > ( I I )

-Fu D +T1G2 J ^

any

Rutilt;

1 corresponds to the rriiixinium oxidation that is possible uithout

iinjujl of oxygen. Further, s,incs the anion latt ice is v/cry

-la-

i.lar in ;imenite and ps&udorutile, this stage can procaud to

simply by the diffusion of metal ion9 without disturbing

the anion latticu itv«rely. This ij not in disagreement with thh

fact fiat ilmsnitti i-> a rather guod tilactrical uonductur. The

second stayu huuouer nttids a cunco'nitant rcoauai of a proportional

amount of oxygen also, further t;ir(;« the anion packiny in ruLilii

and pSdudorutile atu wary liiffurent, this stage must involve 3omo

kind of dissolution and ruprycipitation and must be inherently more

difficult to proceBd.

13. Thermodynamics of a Simple Site Uuenched Hagnetlc Plixture^N.K. Jayyi Bnd K.R.H.PI. Hao")

M vary simple model for a two dimensional magnetic mixture was

studied by the Plonte Carlo technique. Thu model consists of Ising

spins on atoms A and G, qunnchud randomly on a Square lattice!

couplfcd to tneir nearest neighbours only with -3(AB )x3(AA }a.l(B8)

Tha spbeific hsdt ohoub a lambda like) anomaly atH L.*

T c ^ J|<2x-l)| M ,• uhsra T and 11 are the exact tranaltiun temperature1 ' e x ex ex

and the exact iaro field magnetisation of the puce lattice viz. at

x=U. The spin glass order paramdtur / ^a*1")! i& f"und to go as

In | , and goes to zero at T with an exponet >--> 0.25. Thus tha

magnetic phaae diagram in the T-x plane is straight line of parato

f BrromagnBt transitions at T=T »2.3 0/ (< , Bxcypt at x»0.b uhure

onu has a spin ylass transitiun.

It was found that a simple transformation of the Ising upin

variables maps this modal for zero external field to the pure

unsayer model and the exact tharmodynamicB is obtained very simply.

It ie ruassuriny, however, to fin that che agreement with thw

flontti Carlo data is complete. In a finite field thia transformation

breaks Jaun and axact results ara not available. The Monte Carlo

data chow a poak in the susceptibility close to T , but it in

difficult to make definite statements about the nature of the anomaly.

-19-

14. Loiiijjton P r o f i l n i>ludy of Peril and Uofli. (P. Chtiddah andV.C. Ciahni)

In continuation of our studies rt-vartcd laat y-Mr, uis en tM s u r-.• U

thi, Cj<ript-jn (-'rofilBs (CP; of Fenl and CoMl. ThE motivation for th is

work warn thtj con f l i c t i ng charge dunj i t ies indicated by sariiL=r M"1R

and sof t -x-ray s t u d i u j . Our 'neiaiiurdd CP's have been compared with

csJculations baûd on a simple modal in which thu alractrons occupying

the- t rano i t ion mutal d—band are trâtf id uia tha Renormaiised Free

»*tum inodiji, uhil<= th^ ruraaininy conduction elactrons arc treated *a

f r t i i i Tht valuta of wî jhted mean sgu>Jro deviat ion between theore-

t i c a l and ax|jeriiii=ntal p ro f i l es show o host f i t to expurimtmt with

a 6-bdnd occupancy of 7.5 for FeHl ( c . f . 7 . 7 2nd 8.6 by soft x-r.jy

ind NflR situdxt^- r t iup^ct iu^ ly) and 8.3 fo r Cofll (c.f. 9.2 by both tha

ear l ie r s tuo iaa) . Tht l im i ta t ions in our model, and tha i r poabiblu

o f f t c t on thii c onclualonu, haua alô baen studied. Our reuul ts

indicate that the u.jxliur inferances had overestimated the extent of

charjL tranaffer. rtecent unpublished APW calculat ions (of 0.3. Nagel)

also yiue much lower d-band occupancies than thB ear l ier i n f artincu 3.

uf our uor k are undur publ icat ion •

1) P. Chadduh and U.C. Sahni, Phi l .nag. ( i n presa ).

15. Effect of Electron Correlations on the ilectron MomentumDensity in~Holten Flatals (P. Chaddah)

I t has been notud ear l ie r ' that electron corre lat ions ara the

probable cause of the long t a i l seen in experimental Compton2 )

Pro f i les (CPj. Tha well-known ca lcu la t ion of Oanial and Uosko

for a hDmoytneous dlectron gas shows that electron corre lat ions

reduce the d iscont inu i ty in the electron momentum density (CCIOj at

the Fermi momentu*, P f . and also introduce a long t a l l i n i t . I t

i s in te res t ing to axplore the ef fact of corre lat ions on the LCIO of

an inhomogeneouG eloctron gas. Tha problem becomes extremely

complex for a crysta j . l inu s o l i d , but for a molten metal we have

-20-

Ktn <i(,J(' to ^ •<• rf uriii nij'iiur it:al ta l i , uiat l>/ns wi th in a rs-atun.ihlu

f^r ux inia L i on bch<,iiie '

Our a(,,.r.-.acti «t.s unt i a l l y consists of f i r s t -nudifyiny thL?

Rlniitron propayatjr t j include the ef fect of ionic psBudo-

poU=ntialB. Fuiiou/i.ny the work of Rallif.ntine , the electron

self-fcneryy i;j obtained to oiicond ordi'r ss l f -cona iu tent ly . This

modified pru.iayatur, which describaB the impurturbBd state - with

th.j t l bc t r on-Bii-Ct ron inturact ions (ilaying the role oF perturba-

tions - is then uatd for calculat ing the END fol lowiny the proce-

duru usud for a humaytnouus oluctron gas . The numprical results,

abti'iinctj f o r l i q u i d aluminium show that uhereus the daparturrj of

thu t-HO from tht unit stop function i a , for example, 0.05 at D.9 p_

whHn correlat ions aria not included, it. chonyfss to 0.15 at 0.9 Pp

uhc.n those, ird included. CP measureinunts on l i qu id aluminium hsv«

i n i t i a t e d by Suzuki et a l and 3hould halp check our sch^mu.

1) P. Uhdddah and U.C. bahni, Phya.Latt.A 5j&, 323 (1976).2) L. Danitil and S.H. Uosko, Phys.Rev. 120, 2041 (1960).3) P. uh..ddah, Phya.Lstt.A 63, 5? (ig77'J7~4) P. Lnadd<ih, Pramana ( in p r i j 3 ) .5) L. t . ba i lun t ine , Lan.J.Phys. 4£_, 2533 (1966).

16. fcxpurimtin t u l 3tudy of Compton Prof i le of Baryllium (P. Cand U.L. Sahni )

Our prouiau- theorut ica l calculat ion of the L'oinpton Prof i le in

8e had fa i l ud to shou th3 long t a i l which car l iBr experimental resul ts

tfxhibit.ad. Since thisse experimental rosul ts had been a f f l i c t e d by

mult ip le bcutteriny correct ions, which had not been properly accounted

fo r , an independent measurement ui ing our own set up was considersd

dei i i rablu. A th in polycryBtal l ine s l ice was uaed in our measurement

and p ro f i l b sihape uas deturminwd to better than half per cent. Our

measurements, af t i i r applying mult iple scatter ing correct ions, yiaJd1

results ' which ayri=e with uur calculat ions better than the praviuu^

x-ray results d i d ; however, the discrepancy between theory and exper i -

ment p c r s i j t s . «n improvod theoret ical ca lcu la t ion , taki.iy correlat J.rjn

- 2 1 -

into account, ii> therefore orsuntial for under standing the

Lumpton pruf i l t of beryllium.

1) P. Lhaddah, Ph.D. thes is , University of llombay, 1977,

17. L ijjc t£_2Il mnenturo ijunsity in bubsti tutionally Disordered

A1J u y h (I3.

Cletlron s ta tbs in subat i tu t ianal ly disordered alloys have

been studied j j i r d this cjherunt .jotantial and auenye T-'n..itrix

appi ox iiiuj L iun • Thuujh what i-i mo t ufte.n colcultitBd L3 ths

dun^ity of atutfco, complex anaryy band otructurd havd also biran

rticintly calc ul'ittjd . Tha electron roomtintum d&n^ity (EMO) also

curr ias dtt i i i lcd inf urination about the ulectron s t a t e s , and since

i t i s expo rifntntally <nij& jurat ltj, can po^&.'.bly be used to check th •:

Udrioua approximation achonicis. To inveatiyute this idwa, uiu tiaua

obt>jinid this LI'llJ for d model binary s?lloy within the coherent

potuntial appro.-;imatioii . The Hamiltonian of this sinyle-baniJ alloy

is assumed to h.;iue, in tha tic,ht-binding r ipresuntat ion, no

off—diagonal disorder. Thu occupancied of tha Bloch statEia, of tho

rufuruncu urdurtd HamAItonian, have been numorically •waluatail for

a bec latLicu with thu off-diagonal part of thB Hamiltonian haviny

only ntiarubt n..:.yhlMjur oi/driap terms. Our reaults ' for th is modal

alloy uhoui that at juitablu concentrations tha ECIO comprehensiwaly

rbfli-cts both this I'ual and thw imucjinary parts of thu coharunt

putunt ia l .

P. Lhddu^h, J .Ph/s .C ( i n

-22-

I I I . Light acatluriny and Liquid Lrystai Studias

10 La-jut Hainan Study af thu Urder-Diaorder Transition in(NH ) LuLl .2H 0 (H.fJ. Roy, u.L. bahni and PI. L. Banzai)

1 )Ammonium coppar chloride dihydratB exhibits a broad

upucifie heat anomaly between 120-2UU K attr ibuted to order-dis-

order of ammonium ions. We have made a detailed laser Raman

study of this t rans i t ion. Interest in this compound arises due

to tha nature of i t s ammonium network. Along I axis the adjacent

ammonium ions are at almost the same distance as in ammonium

chloride, but in the X-Y fjlanu intervening copper-water clusters

enhance the separation by XX ^0^. From the point of ordering

(dominiintiy duo to octupolar interactions d.Tionyst aiiuiiuniuui ions)

the system thus behawaa as 'quaai-one-dimensional'.

Ulykuff det.ignatet> the room temperature (300 K) apace group14

for this crystal to be 0., , but no cryatallographic data exist

for the fu l l y ordBred state (beloui 100 K). Us recorded polarized

Raman spectra at both 300 K and 100 K, using a 50mlif He-Cd laser

(4416A) and a double monouhromator (both made in our laboratory)

with a spectral band pass of 2.5 cm . Thu sptxtra at 300 K14

(disordered phase) are consistent with 0. , but nBu modes appear

at 100 K, implying a loweriny of crystal symmetry. To establish

tha lat ter we considered each subgroup of 0 . u/ith the help of

a symmetry vector calculation (that indicatod possible frequency

ruyions uherb new modes could appuar) we could establish that a l l

subgroups, except 0 , arts inc.ondit.tont with observed features.2d

find 11/ £>ite symmetry conbidtiration mere used to pinpoint tha

space group at 1Ou K to bo U .

2d

To investigate how 'i^uaoi-une-dimfan sional ' character j f f t jc ta

the euoJ.ution of long range uruer parameter m ( in contrast to what

is found in NH Cl) uu studied the temparatura variation of the

spectral intensity of soma selected mudes. (See Fiy.16.1).

(m denotes the difference in f ract ional number of awnunium ions

in the two possible orientations, j Tullouiing r t f . 2 onu can show

-23-

that in tens i ty of modes (a) and (b) in Fig.18.1 varies as (rt+mB)

whilst for mode (c ) i t uarius as m C . Thus m can ba obtained in

each ca iu . An auarayu of thasa results ia compared ujith that

ootainod for MH^Cl. (Fiy.1b.2>. Luidunt iy, the much slower

100 Ul> 2X1 100 KO 200S H I F T < C m " ' )

f iy .18.1 Tt3.npurai.urt: va r i -ation of btok«a Human Spectra.

uauid be eot^bii^hed formadtib (a ) , (u ) ••ind (u) only.Note Sijtlib chuOtjdU •

-1.0

NHjCI (from Rtf. 5;

0.1 0.1(T/Tc)—^

1.18.2 Comparison uf/diu«;_. ofr (NH ),,0 and NH LI. '

change in m ualues for our case is a reflection of the

dimensionality of the system.

1) H. Suya et ai., Idull. Chun, bot. Japan 3£, 1007 (1965).

2) J.l'l. Lovuiuck and J.B. Sukoloff, 3. Ph/8. Chbfn. bolida

34_, d69 (1973).3) A.R. 5harp and M.h. Pintar, Lham. Phyii. Ijj., 4J1 (1976).

-24-

1 9 Laser Hainan ^tudy in Lha I'iixod (DoubleJ baitsI INH ) K T* LutT~T7Fnj (,1'I.L. liansal and U.t. Sahni )L 4 1 -x x J 2 4 2

A lawtr Ka./ian study in the mixud Sjyjt&m [ (NH j K 1 .*- 4 1 -x x J 2

LuLl •2Hi.(J has btien made u i th a two fold ub J U L t i u t . F i rs t ly to

ex am ilia huu a normal modt, dufliinant j-y inuua.uiny one ^ub- iat t ice

motion, y«ts modificJ uihfcn tha sanib i uL ia t t i cu is &ubstitutud for .

Secondly, to utudy the chanyao in riydruyon bundt. li-H C l ( l ) in

th is system.

14Th<* parent compounds Dolony to 0 , with tu/o molecules par

uni t ca l l and posses d[i Raman autiua moues. Polarized Raman

spectra uiare rucorded using a 5(JIIIU He-Cd iasar (4416A) and anulysyd

atiiny a double monochromator with a spuctral band pass of 3 era .

Tha 8 modts ara uery strong and appear in the pure ammonium

compound (X = LJ) at 92, 117, 198 and 1532 cm valua=s. 5inco th is

c rys ta l cdn uo vieu/ud <u chains of" NH.C1 (along / d i rec t ion) and

the 19U cm mode id c iost to and similar to zona boundary mode in

NH LI (around 1t)0 cm ), uiu examined thfa apuctra of dbuteiratad sal t

to ascertain ttiu tiuhxviuur of this moiio. ~ihu B modus in t.h.j

Uoutdratad sai t uiura uLuurvud at lJl, 115, 1 cJ4 and -iOb. This shou?

that bJ2 mode it) u uatar l i b i ' a t i un . Further, from the ubsbrt/ud-1 -1

s h i f t of 1 yu ci» mode to 164 cm unt wt i t juant i tat iudly establ ish

that th is i1yu era ) modu predoiiiindntly contains translat ions of

NH - which is tha suulat t ice inuolued in mixiny procoss. The cun-4

Cciritrdtiun dapendeftcci of thi& muda is bhou/n in Fig.19a that c

the 'two-mode behauiuur ' . Mnaiy-iif uf the ruou l t i

fol lowiny Htl mudbl of bauhoffer et a i ' ^ indit.ot. = b that sum of tha

iiquared frequencies uhuuld vary i i nuar l y wi th x . This i3 indeed

found to be the case

Ue alao studied the x dependence of the about' water l i b ra t i on

so as to dsterminu the changes in the hydiOytn bonds O.H C1(I)

in the present syatem. The ous&rued x var ia t ion , summarized below,

-25-

yuits that Chu 'af fect ive i o n i c i t y ' of U ( l ) ' s is XoutT in

tliu I\IH aa l t .4

X

- 1i n cm

U

b28

U. I

bJ>2

0.

5.1

a

t i

U.41

541 54 5

U.61

54 8

U.81

554

1 . 0

5(10

no }TO no ijo no* — SHIFT (cm1)

(a ) Hijinan SoecLra fur e,nind linked cry( b / P lo t Ot' Sulli uf b>jUdfcd f'T fL|l4u-ril-i •

1) H. Suyd Bt a i . B u l l l,hera. boc. Jap^n ^8_, 10CJ7 ^ 19GS J.2) U. B a u h o r f u r ut a l . Phy3 . ^ t a t . b o l . 6 J (b ) . J85 ( 1 9 7 4 ) .

-26-

20 Tcmparatura Dependence of Hgtational Lorralation Function inlyclohexdne (M.L. Bansal and A.P. Roy)

A study of tha rotational correlation function ia necessary

for obtaining, a detailed understanding of tha dynamical processes

in liquids. In cyclohexanu (C H ) nibaauraments ' o n temperature

variation of correlation time exist for the V^ , and y depola-

rized modes. Tha analysis for these modes, however, is complicated

by the fact thJt there it> no satisfnotary method of oeparatino, the

effect of uibrational relaxation from the raorientational motion

and further thare is no unique axis of reuritntation. The V

(jolaribad band of L-,H1 _ prouidea an opportunity to unambiguously

study tha reorientation uf tha aymniBtry axis uf the molecule. u-r

hduu infidb such a study in the liquid and plastic pha^a of C H •6 12

The sample was illuminated uainy a 4Qmlil He-Cd lajar (

and the scattttrud light uas analysed using a double inunochrama t or.

The polarized (1 ) and dapolariaad (ly ) band profiles were recorded

ouur a ranga of 1UU cm from tha cantrti of the ba,nd; the instrumental,

half-uiidth being 1.7 cm .

Fig.20 shows correlation functions at aeuHral teroparaturus

obtained by fouriar transforming the data. At 340 K, free rotar

bahauiaur extends upto 0.3 psoc ( 't*^»U.4}. The correlation tims

X* defined aa tha integral of C t(t#) yariss. from 1 to 4 in the

temperature range 340 K - 195 K. In contract to this, Bartoi and

Litovitz obtain an order of magnitude variation in the correlation

tima (ostimated from the half widths of thu bands). We btliove

these differances arise due to the reasons mentioned earlier.

By approximating the C H moleuul'i ac a symmetric top

(asyminotfy parameter ^2 —0.42), corruiation functiunj have buen

computed uaing the j and Pi diffusion matluB . Ha an illustration

uu shuw comparison with the 34u K results. In gunarai, the

1*1—diffusion mudel repruducas thd axpariniantal curves better and

givas f * coiiiparable with the experimental vaiuea.

- 2 7 -

-0.S -

8 -1.2 -

0 0.5 1.0 1.5 2.0 2.5

E«pt.Fre* rotorM-DUMB* 3)J-Ditf. (B*4)

-1.6 -

-2.0

Lxperimental rot i i t ionai correlation function in cyclohux.ineat oeueral tempfardtureo. i^o.upjrison u/ith extended d i f f u -sion modal calculation is presented for j4 0 K.

1 ) F.3. Bartoi and T.«. LiLuuitz, J. Lhcu. PhyS. 56, 4U4 (1972).2) J. Schulz, 2. Naturfarsch, 2y.a , 1636 (1974 ).6) R.t.O. I'lcCluny, Adu. l*lui. Rei. I n t . Pruceooes: 1_U, 83 (1977).

-2B-

21 . DiHiirijt-rad Liquid Crystalline Phasn In thtj Cum|joundb,p-n—rtlkuxyuVnzylidenn-p—urolnoBunzcjl e '<r ida (K. Usha Ounii,

)

The hiyh temperature omectlc phauuj uf thti haxyl, huptyl,

nonyJ and tutraducyl member:* of ttw serins u( compuunds, C Hn .

O.C H, .OH = N.C H .CUUH haws bean dof ln i te iy identi f ictf to bu tha

smHttic L phd&e^ (disordorud, t i l t e d Bmut-tic phases) from our

texturu studins , The tranait iun tbrnpuraturua otitulnLd far tho

S —N tr.-inbit.ian fru-n our Q-JL scans compdr d ueli. with the tsmpiira-C 2)

tures c.iici.iatud for tho S -N transi t ion from OcPlilien's thuory ' .Houuutir, tha transition entropibs., ^ 3 cdiculaltjd from this>

thuory do not ayree with tha valatm of &S otitained in our

ex per imEnts. This hat. been attributed to thu additional rotational

ordur uf thu S pha^« (nut prebant in tha b phatie) which is lostC 1 \ *

ot the S -N transition ' .

Prbliminary X-ray diffraction work has baen carried out with

tha nonyl member (MBMB<>) in the S and nematic phases, so as to

determine the tum'peraturu dependence of the smectic layer thicknoaa,

dr the t i l t angle fl , and the intfc -molecular separation, 0. It la* o

found that d is about 3U 1 in th; S phase and increases abruptlye

to 35 t\ Rt the 5_-N transit ion av ??7°C. 6 has been calculated

from tha ualudS of d, using the relation Cos9. > d/L where L hast o

been taken to be the length 'of the dimeric form (48.2 «) of the

molecule obtciinej aucording to De Uries modal . 4 is about 50°,

autiy from the S -N tranait ion, but decreases to a smaller value atL 0

the t rans i t ion . 0 increases with increasing temperatures (5.0 Ao

to 5.3 A) in tho 5 phase. The nematic phase is found to be a

..keued cybotuctic one (where S typu order exists). The 5 -type

order, does not peruist for a larye temperature ranye. The value

of the molecuibr ienyth, t , as obtained frcro our X-ray results in

- 2 9 -

the rid.natic phaja i3 found to bs V 42 A, showing that the

diraeric form of the molecule is prbsent in this phase also.

1) K. Ubha Oanii, A.S. ParanJpB, P.S. Paruathanathan, E..B. Plirza,A. I . ' Ctehta and K.S. Pat e l , to be published In the Proceedingsof the Nuclear Physics and Solid Stata Physics Symposium (DAE),Poona (1977^.

2) W.L. flcflillan, Phya. Rev.* £ , 1238 (1971),3J *.D« Vriea, rioi. t ryst . Lit). Cryst. 1J_, 361 (1970).

22. Structural Study of the Saiectic H Phase of HxBPA (6 0.3)(K. Usha Oenia, A . I . Mehta* and U.fl.K. Rao+)

I t is only recently that the long controversy that existed

about the nature of the Smuctic H (SH) phaSB (thought to be a

since tic B phase unt i l recently) uas resolved, as a result of

careful miscibil ity experiments which proved that the 5 and 5H B

phases wars different. X-ray diffraction work had previously 3houin

that the structures of the two phases mere indeed, quite different .

While thu S phase uas known to have a hexagonal packing, ths 51 ) 2) "

phaae, both in TBBA ' an also in 7 0.5 ' (a hiyhar homologue of

HxGPA in the series of compounds, mO.n) uas shown to haue a

baao-centerud monaclinic l a t t i ce .

To check on the structure of SH phase ' of HxBPA, the X-ray

diffract ion iines obtained with this compound at room temperature(supercooled & pha3e) haa been indexed, assuming that i t has a

H

c-face-cunts -ud monoclinic lat t ice with two molecules per unit c e l l .

In such a structure the reflections corresoondiny to h+k = 2n+1 ,

where n is an integer, ara missing. Thu c-axis uas taken to be

paral le l to the iony axis of the molecule and hence ft =(fi + 90°) ,t 3 j

where fi i3 the t i l t angle and is about 34° at room temperature .

Good agreemunt betuutn the obaerved and calculated la t t ice

uaa obtained by takiny the followiny la t t ice parameters:

a m 1Q.5 A, b - 5.U A, C = 23.B S and ^ = 124"

-30-

°3Thti volume of tho unit cell is about 1036 ** , and this luads to

a density of 1 .1135 ynio/cc. This, result is in complete disagreement4 )

uith the valu' oT 1.2 to 1.3 ym^/cc obtained for the density in

the S phase, assuming a huxayonal packing of molecules in theH

smectic

• Bombay Uniuer&ity Studfcnt.+ Chemistry Division.1 ) J. Ooucet, A.M. Lewelut and M. Lambert, Phys. Reu. Lett. 3_2_,

301 (1974).2) U.H. DeJou and J.A. De Poorter, Phys. Lett. 61_ rt, 114 (1977).3) K. llsha Deniz, U.R.K. Rao, A.I. fiehta, H.b. Paranjpe and

P.S. Paruathanathan, Plol. Cryat. U q . Cryat. 42,, 1137 (1977).4) K. Usho Deniz, rt.l. (<lbhta, U.R.K. Rao, P.J. Parwathanathan

and *.->. Paranjpe, to bB published in the Proceedings of theNuclear Physics and Solid State Physics Symposium '™»r*Poona (1977).

-31-

IU Other Topics

23. Ri.isist.ivta Stataa in Superconductors» (G. Qharmaduiai andB.rt. rtctn^m**)

An ext«=ni»i\/e study of oeutral aspucts of the currant-inducyd

rcaistii/e states of thin film superconductors with special

reference to Ag-bn pruximity-efftct bridyoS has been carried out

Loth undur thurn-Jl equilibrium and nonequilibrium situations. A

fbu siynifii.dnt observations are liotud bslou whereas the detailed

d=ta anaiysib to draw specific conclusions in underway.

1. ri sy^tumatic dectuauu in the bridge critical current is

otjatrved undur phonon injection from the heated transverse

njrmal metal strip.

2. * jump occurs in the bridge critical current at T a T^

(the lambda paint of helium).

3. Hysterusib is observed in the current-voltage characteri-

stics of thede bridges which increases as the bath

temperature is luwered.

• Work dune at TIFfl, Bombay.»• Staff Flember at TIFR.

24. Solid State Phenomena From the Standpoint of FunctionalAnalysis (R. bubramar.idn and K.U. Bhaguiat)

Often on8 has to deal with unbounded operators. At times e

naiue analyaiB seer,is to lead to certain paradoxical results (for

example, the Klauder Phttnomenon). The controuertial "Stark

ladders" is another example, where a continuous spectrum due to

uniform electric fifld is turned into a discrete line spectrum by

a periodic perturbation. A feu years back ue studied the rBiiiti-

uiatic effects on surface and impurity states and had observed

that there exists a relatiuistic impurity state merging to a

-32-

band~«dyn in tha non-relativistic limit. No such state was

obtained in the surface stato prcjcitm. In thu liijht of Cbrtain

new results due to biinon we haue undertaken the study of this

phtnomunun from tht standpoint of functional analysis. Our

preliminary observations are presented at the Nuclear Physics

and Solid Statu Physics Symposium (D'*E), Puna iy?7.

25. A Simple Proof of Signer's Thaorum (R. Subramanian andK. \!.' Bhayuiat )

This is a by-product of our oarlibr uork on operator

inequalities. «ccordiny tu Wiyner's thoorem "if «, B and C are

poditiue operdtors than thu product ABC in positiue if it ia

Hsrmitian. Threa proofs of this theordm are knou/n in the litera-

t.jrii. uiu have giuen a puruly algeuraic dnd by far the simplest

prouf of this theorbin. (To bo pubiiihsd in Proc. Ind. Acad.

be. i

2b. Extension of Inducad nonoinial Haprbjentation Theory tobcmi-Jirm. t Product Groups ( I . u . l / . rtdyhauachdryulu)

The monumial ropresentation theory of ordinary groups has

been uxtendfcd to iami-diract product yroups.

L=t P l> G be a yiuen aemi-Uirtic t product group in the usual

notation where Q i s a normal subgroup of P > G and the factor

bic.jp P > u'/G 3 P( =. stands for isomorphism). Let Q (?• H be a

iubijroup of P t>C such that UC P and HCG and Hq = H for a l l

•) £ U which follows from the de f i n i t i on of the s»mi-dirtict product

Now, consider the ordered sections S = (g-j i • • • • .9^) and

T = (P1 ,Pn) of P and C w . r . t . U and H respect ively. One

that an ordered set of coset repr=sentdtive elements

of P !?G u.r.t. Q l>H using thd ordered oroduct T S ordered in thuP ^ G

usual may. Hence, consider (U ^ H ) ^ the induced monomial

- 3 3 -

of P fc* Li from the subyroup (U |>H) making usu

uf a huiiiu.norphism $i M t>- H —^ (tj ^ Ô i * ' UB Jtudy the structure

of ( j P> H ^ which yentral iztu in a natural way the induced

thuory of stmi-diroct product yroups. The =>tudy

of part icular cases of the about* induced rapreodntation and their

applications ire beiny studied.

1) n. Hamermbsh, Group Thoury and I ts rtppiications to PhySicjJ.Problems, London, Mdditon-Wesley, 1962.

2 7. Gen^r^liêd lionpniidl Rbpreountations and Thfeir ftpplications

Tht generjlizod monoini<jl representations ace found to be

central for diuttraB applications in m Jthematical physics . Hurîn

u/u indicate a now applicatiun of them which l&ddt> to s i ,i(,lif i cd -

tions and a*tensions. Let G be a gioup, H a subyroup uf G uiith an

ordered iu f t section l g . / i € - U i I Bomu suitablu icidax set,

end <fl H -? HJ a group humoinorphisin. Let the corresponding genera-

l ized monomial rapresantation of G bu yil/un by H J ( S ) . First ma

note that ouury transitiv/e monumial r upresent at ion of G is J

generalized uionoiuial rGpresentatiun and uonwarauly .

To consider tile appl icat iun, uia ahall 2t.tcjblish the lackey's;

Subyruup theorem in terms uf the ybneralizud muriomial ra^rea^fitJ-

t iur is. In tht> auouu notation lut K be a suDyroup of Gc r

th« bet uf matrices Hj/iSJ^K. To analysd Hv(S)J'K.iiie tiute

that i t ntiud nut Ufa ênevîlly t rans i t i ve . Hence, uid deuampus-. i t

in to t ransi t ive components. To specify each une of the tronî t iue

components, we cunaidur 0 the set of d is t inct Ht!K duublu coauts

uf G. Lut Hak6U. I f a . , a art, the d is t inct rfcprea = ntdtii/<J

from the double co&uts 0, we haue U Ha.K = 0.

Muu, consider a l l the H cosets cf G uhich l i e in HaK. Let

ba yivyen by H , H , . . . . , H . Further, le t I = Ha C\ K.X1 *2 Xn

- 34 -

In tUu atoi/e notation i t

( T ;

uht.ru T io a out uf di^Lint-c lut ' t caout.) of L in K. The

^ i ) and ( i i ) uhun J4 ib rcoLr ic t t id tu rndtrix rutjrus

i s KriuWn a^ tive T'ldCKty's i»ub-yi'uup tridaroin.

I'I. Hji'ibiinesn , GruuiJ fhtur1, and Its "^ylicatiuna to

FISSION PHYSICS

-35-

PHVblCS

It is well known that the rare mode of fission accompanied

by liyht charyed particle emission is potentially capable of

throwing much insiyht into the nature of nuclear dynamical motion

particularly in the last stayes of the fission process. However,

both because of its low probability and a large number of corre-

lated obseruables, this raude of fission has not be studied in full

detail so far. The fission Physics Section has concentrated on

the studies of this muds of fission in the recent years. During

the year covered in this report, most of the experimental investi-

gations carried out in the section relate to fission accompanied

by liyht charyed particle emission. As can be seen from the

detailed write-ups, these investiyations have brought out many

new features and correlations, which should be taken into account

in any theoretical analysis of the process.

As in the previous years, tha theoretical investigations

carried out in the section cjver various aspects of the fission

process, heavy ion reactions and uther related areas of

physics.

-36-

1 . Multipardiiiot'T studies of fragment Waas. Lnurgy andCorrelations ip Long riancie rtluha Particle AccompaniedFission of ^-"U Induced by Thermal Neutrons (R.K. Choudhury,a.n. Nadkarni, P.M. Rama rtao and J.S. Kapoor)

Detailed experimental correlations of fission fragment

kinetic energy, rnasa and alpha particle eneryy and angle ware

obtained by usiny a back-to-bacK yridded ionisation chamber for

fission fragment energy and angle measurements and semiconductor

detectors for alpha particle energy measurements, A thin source

of U (10 <ug/cm ) depDuited onto a thin VVNS foii uas used as

the cathode of the parallel plate ianisation chamber. Tuio semi-

conductor detectors u/ure mounted at the back sides of two

collectors with thin Ml windows to dettct lony range alpha (LRH)

particle alony the eluctric field direction of the ion chamber.

The pulses froin thd two grids, two collectors and LRfl datsctor

were gatud for ternary events and were recorded ewunt by euuni. on

s magnetic tape by means of a multiparameter ddta acquisition

system. Binary fission events mere also recorded for on line

calibration and comparison with ternary data.

Fission fraymfcnt energies were calibrated from the known

energies of tha most probable binary heavy and light fragments.

From the energies of thd pair fragments, the masses of the tuo

merB obtained from the mass and momentum conservation

. Grid pulsa height distributions uere used to determine

the angle ©• of the fr^g.nants 'jith respuct to the ulectric fidld

direction from the foilouiing uxpre^aion connoctiny grid pulsa

height Ug and fragment kinttic energy t, :

wht:re H* is proportional to the frjynunt ranye and d i^ yrid-cathodii

distance. Thu Lon^tants uF th= abuve formula wuro obtained by thu

known yrid distributions in binary fission.

-3V-

Fiy.1 .1 shuua the mass distributions mua^urud for binary

and ternary fissiun ca»eo. Fiy.1.2 stiou/S the uos=ri/ud t/aridU

2000

1(00

J2uoo23

u loo

too

0

-

ik

,, -*&•'

•

•

••• BINARY•""IRA

.V

•

. * ' • •

w *

»*

• • 4 - 1 ^ * U . .

CO 80 100 120 U 0 ISO

FISSION FRAGMENT MASS, AMU

Fig.1.1 Binary and LRA accompanied mass distributions

12 U II II

LRA ENERGY(HtV JFiy.1.2 Total frayrnont kinetic energy E versus t-u

of total frayment kiniit ic entryy £ uith LRA eneryy t ^ , uihicli ha=.

a slDpa of -0.3U6 a= compared to —0.4 obtained by earl ier u/ork of

Gazit et al . The obsurued must (jrobabla ualuijs of LR« any-Le mith

-38-

to the light fragmsnt, { ., versus LRA endrgy, £K artt

shown in Fiy.1.3. Fi^.1.4 shows tha valuB of 5 ^ L for different

liyht fraymjnt na^B^. It is jt*n that 5 ^ ^ IncceaiBj with nais

A.

10 it u u it it n i« itC«A ENERBr E.,IHcV>-

Fig.1.3 LRA anyla with light fragment ©-Lversus

•i to I IIMH1 MAtMENt HAS 1 . AMU

tog

Fig.1.4 Host probabia LRA angla •<*. varsua light fragment maas.upto n a 90 amu and rumains constant for higher ina seis. Thi* roault

doea not support any of the two provious ruauita of Carlss at al /

and Gazit at al '. All the above correlatiana and other detailed

corralations which can UB obtained by thu multiparam&'ur data are

bein<^ analyzed by trajectory calculations to obtain informatiun on

conditions at thu instant uf LRA emission

1 ) Y. Gazit, M. Kata»u, G. Ben-Uauid and ft. Morah, Phy«. fiav/.C4, 223 (1971).

i) C. Carlda, I'I. Aeghar, T.P. Joan, K. Lhastui and U. Signarbieux,Proc. on Phys. and Cham, uf Fission, Vienna, Austria (1969,),p . 1 1 9 .

-39-

HuJLt_ijj.lip_itX- -JistriLution of i'runpt Ganwiu Maya in Lpun IoneJUSTernary Fisajjn uf "*-5fLf (U.K. Lhoudhury, O.L. Mohanakrishnaand V.i.. Ramaraurthy )

Study of thu de-excication pruLu^s of fiosion fray,-n=;nts and,

in particular, thu ineasurbinbrit of the multiplicity distribution

of yamma rays, provide important information on thu properties of

thd excited fraymsnts. In the prasent work we have carried out

measurements of the first and Second moments of thd ydmnia ray

multiplicity distribution in turnary fi&uion ay multiple coinci-

d»ncd tuchnique. Thb i xptirimental method is similar to trut

adopttid in HEf.1, faxcopt that the semiconductor dut=ctor ufas

employed to .neaoure tha aneryy of the light chdrjod particle (LCP)

emittdd in ternary fission. Loinciddncey uibru taken batuxian thu

LCP detector and any onu or both the yam 1a ray detectors. Tha

coinuidoricu gates were usud to yatu the LCP spectra to different

4udrtar3 of an analyser mdinory. Kro.ii the counts pdr Lhann^i for

the oinyiei, dauuld coinndtincas and triple coincidence, it uaj

pooiiible to obtain thu multiplicity distribution pdramotar^ a.-, a

function of LLP enaryy. Fiy.2.1(aJ shouj tha LCP tneryy spectrum.

The oDsoruud uariation Df n and f as a function of LUP endryy,

aro shou/n in Tiy.z.1(b) and Fiy.2.1(c). It is suen that n is

almujt conbtant with LuP tnargy in di8agr{!8mdnt u/ith the earlior2)

result of Ajitunand . The uidth of the multiplicity distribution

aljO does not show any variation uith LCP energy. Hou/euer, the

absolute ualue of g~ av/crayed over LCP snergy is found to be

about 20/i to iQf, laryur than that for thu case of binary fission.

Thin result can bs interpreted to imply that tha fragments in

ternary fission havu a smallar ai/t-r.igG apin aj compared to that in

binary fission. Thti near constancy of «~ uith LCP enaryy

indicates that thu position of LCP d.-niasion and thd interfrd

distinct: at suission are not intercorreldted. This has got

-40-

importJnt i.nplicutiuns on the rajjlt^ of various trajuctary

calculations which ara carried out to deriue information on

scission paramutur^.

BO

T O

4.0

100

?i

80

~28o

z

3 12

• * •

1

H, f »{ | l {J

•

B 10 12 14 16 18 20 22 24 26. LCP ENERGY. M«V) .

fig.2.1 (a) LCP energy spectrum (b) Average number n ve. susLCP eneryy (c) Width t~ varsus i.CP energy

+ Published in Pramana Mai 9, 62J Qac (1977).1) U.S. rtamd.nurthy, R.K. Choudhury and 3.L. Clohanakrishna,

Pramana Vol.8. Wo.4, p.3i!2 (19/7;.2) N.N. Ajitandnd, Nucl. Vhy*. A133, 625 (1969).

3. Uuantitatiud Heaolution of Th-Anowaly+ (ffl, Prakash andU.S. Bhandari*)

Fur Th isotopes thu calcuiutdd fir^t saddle and second minima

of the double-humped barriur are abuut 3 Wan iamer than the expsri-

raantal VdlubS. In an attempt to rejolve this "Th—anuraaly" in terms234

of a third maes aaynimatric minirnuin in tht fission barrier af Th,

Sharma and Leboauf ' hava calculated the fission penatrabilities

through a triple—humped barrier and concluded that while the

-41-

Sub—barrier fission resonance structure is successfully explained,

the punctrabilitias are too low when compared with those throuyh

the double-humped barrier proposed by Back et al . Since such

lou penetrabilities throw tht fission probability fit of Back

et al, completely off, we nave performed penetrability calculations

throuyh a triple—huropeii boifiar whose parameters arc consistent

with the Th-anomaly as well as other recent experimental

evidences ' . It is shown that one can obtain tne correct

penetrability by assu.niny that Back et al actually determined the

parameters of the swound saddle, third minimum and third saddle

for ^ Th from an analysis of th=ir (t,pf) data. The height of

the first saddle is assumed to be that yiven by microscopic

calculations for this nucleus. Barrier shapes used in the

Back et al Sharina & Prakash andLoboeuf Bhandari

a) b)E 1, w1 6.1b,1.0 6.15,1.0 3.0,0.5 3.0,0.5

E 2, w2 j.1,1.0 3.1,1.0 2.5,1.2 2.5,1.2

E , w 6.5,0.75 6.&.0.33 6.S.1.U 6.15,1.2

E^, w^ - 5.5.U.23 3.1,1.0 3.B5,0.5

E c, u - 5.8,0.31 6.5,0.75 6.2b,1.0

present uork (sea table above and ref.5) are consistent with the

Th-anamaly as well as other recent evidences in favour of a third

uell at a deformatijn much larger than that of the second well.

Hlso, they explain tha sub-barrier fission resonance structure of

Th and provide a quantitative resolution of the Th-anomaly

in terms of a triple-humped barriBr.

+ To be published in Ph/a. Rev.L.* Visitor from Pohiavi University, Shiraz, Iran.1) R.C. Sharma and J.N. Leboeuf, Phys.Hey.CU, 2340 (1976).2) B.H. Back tit al, Phya.Rav.C9, 1924 (1974}.3) J. Blons et al, Piiya.Hew.Lett., 3_b, 174y (197b).A) J. Caruana et al, Nuil.Phya.A285, 205 (1977).5) fl. Prakaoh ^nd B.5. Shandar.i, Phys.rteu. (to be published^

-42-

4. Analysis qf Fragment MriLjldr Distributions in fissionIndue fed bv Heavy Ions (Rekha Uovil, fi.K. Choudhury andS.S. Kapoor)

The fission fragment angular distributions in the fission197 209

of Au and Bi induced by B,C,N and 0 ions with bombarding

energies in the range of S to 10 flev/nucleon measured by

Viola et al ' have beun analyzed by us in terms of th» statistical

theory with the following aim in views How do the values of

1 characterizing compound nucleus formation determined fromc r i t

the analysis of fragment anisotropy data compare with the

eystamatics of 1 -,. from heavy ion fusion cross-suction data?

In the present analysis of the above fragment anisotropy data,

the values of 3B f f ( * /*»!) calculated by the rotating liquid drop

model are used as inputs. Contributions from multiple chance

fissions art) taken into considerations by calculating values

of f{" I f^. (*»*» 1c r i t»

Ex) "

3ln9 ths level dsnsity formula

developed earlier^). Assuming that fission is contributed only

by 1-waveB upto a maximum of 1 .. (which also from the compound

nucleus) the sum of fragment angular distributions from fissions

occuring at different.stages of da-excitation era obtained. Tor

each cast the value of 1 uhich reproduces experimental aniso-

tropy is then deduced. Ths values of 1 .. deduced from fragment1)

anisotropy data are compared with the Bias medal ' for the calcula-

tion of 1 . which is based on ths observed systematic* of heavy

ion fusion cross-sections* The results of present analysis show

that valua3 of i c r i t can be determined,from simple measursorents of

the fission fragment angular distributions.

1 ) Viola at al, Phya.Rev. 129, 2710 (1963).2) 5.K. Kataria ut al, Solid State Phys. k Nucl.Phys. Symposium,

India, 1977. '3) R. Bass, PhyS.Lett. 47B., 139 (1973).

-43-

5. Transmission Through Blharirunie Oacilxator Potentials;Application to Oouble-Huinued, fission Barriar* (fl. Prakash)

Exact penatrabiiity calculations throuyh a duuble-humpsd

barrier (OHH) whose •ucond well or the Second barrier has been

taken to be bihormunic in nature, have been performed. Tha solid

curt/6 in Fig.5.1 shows the potuntial enurgy curi/u of a UHB whoje

second well is biharmunic and the Hotted curvu ihoua a barrier

fur which tha harmonic curvature parameter of the second wall is

2 ti u w,/(w_+w_). Penetrability calculations throuyh auch a

barrier madu Ufl of three parabola* raueal that thd transmission

is roughly the samt as that throuyh the biharmonic barriar. The

position of tha second wall of auch a biharmonic; barriur shifts

to the riyht as shown by tfA in Fiy.5.1. The shift (<a,-Ca. }

incruaaaa with thu ratio ( w^/ ^ w ). A laryur value of £ x

inuans a larger valua of the moment of inertia pararnutdr (21/ H *" )

for the nucleus in the second well. A typical 15^ fractional

increase in the position of the second well leads to a 31 fract-

ional increase in "I" in the solid-nucleus model and a 3U^ fract-

ional increase whun the nuclear rotation is considered as potential

motion of an ideal liquid in a riyid rotating Shell. A much larger

fractional increase is expected on tha basis of the more realistic

superfluid model. Penetrability calculations throuyh a OHB uho.se

second saddle is taken to be biharmonic shows that the salient

feotuces of transmission like the resonance structure and the

order of magnitude at transmission are more or le=>8 preserved.

Thus it is seen that a family of fission barrier shapes exist

which give roughiy the same penetrability as that through a UHB

made up- of harmonic wells and carriers. This leads to an

uncertainty in the position of the barrier uxtramd as determined

from an analysis of the experimental data on fission probability

and angular distributions.

-44-

4 -is

LJ

u. 2

QO 02 04 08DEFORMATION

Fig.5.1 Solid line DHB with biharmonic second wall. Dashadlina DHB with curvature parameter for second wall

• To be published in Journal of Physics, Gt Nuclear Physics.

t. TfSO Response to frawnonts from Light Charged ParticlsAccomaanlsd fission of "°\J (N.N. Ajitanand, K.N. lyemand S.H.S. llurthy)

lyanyar

In this study uie haue u6ed the TfSD (Thin Film .Scintillation

Oetuctor) to detect the fragments in light charyad particle atcom-

lanied (LCPH) fi3Sion. Thu TFSiJ pulse heiyht distributions obtained

due to binary and LCPA fission fra3menta ara shown in Fiy.6.1. It can

be seen that thu peaks in the LCPA fission are shifted to low&r

channels as compared to thu binary fission peaks. The peak to valley

ratio in the LCPA fission distribution is significantly larger than

in the binary case. To interpret these results the response function

of thb TFbD bajed on an expression for the specific luminescence

was used. The pulsa height calibration was done by calculating thefi B

response L. and L using the values of £/ft and i- at the most probable1. n

-45-

11 yfib and heavy fragments in binary fission and assigning them

CHANNEL NO. - '

Fig.6.1 TFSD puXse height diatributions for binary andLCPA fission

to the corresponding peaks in the obsarved TfSD pulse heiyht dis-

oiny theLCPA LCPA

tribution. The LUP* peaks then gav/e L, ,and i-u ,L n

known information on the eneryies of binary and LCPA fission

fraymenta ', the TFSD data uas analysed to obtain the ft and I of

the must probable light end heavy fragments in LCPA fission.

The ualuee obtained for the LCPrt fission fragment masses and

charges are given in Table 1 . The errors indicated are for a 5%

uncertainty in peak channel assignment in tne TfSO distributions.

Results show that compared to binary fission, the LCPft fission

masses and charges are more shifted for the light fragment than

for the heavy fragment. A possible interpretation of this result

is that on the average the light fragment contributes more often

to the formation of the LCPA.

-46-

Table 1

EyaluatIon of frajmapt properties by cornbinintemiconductor an,d TFSQ msaauramants of ^

Moat probabls l igh t dost probable heavyv/iiluaa fr*umant valuee

amu (rieV) (F]eV)

Binary 96.06 37.76 100.42 139.14 54.24 69.91f issionLCP* f i 92.5 35.u 92.82 1.J3.5 55.0 64.77

+1.U +Q.d +1.U +Q.8

1) N.M. Ajitanand, Nucl . Inatr . 1 Hath. 143 (1977) 345.2) '.Gazit, •*• KatdSi, G. Ben Oauid and R. flaroh, Pbye. Rev.

C 4 (1971 ) 22J.

7 - tmisaiun of. Enermtic LXyht Chargad Particle (^»1.2) Infast Nautrun fTatiljfi of Z35U (0.I1. WadkJrni, R.K. Choudhury,j . 5 . Kapoor, P. Krishndrajulu* and G.K. Pbhta*)

The object of the prasant work uias to compare the yield a

energy spuctrum of prutons, tr i tons and alpha part icles in f ~uiaue

neutron f ission with those in thurraal (a-uawa) f ission of U .

finsion fragments uera dstdcted by muana of an ionizatian chamber

whose cathode was coated with a thick (*» 5 mg/cm ) U source

ind individual l ight charged particles ware detected by means of

i A £-E semiconductor detector talescope, the thickness of A t

and t detactors beiny 63yU and 5UUM respectively. The coincident

A i- and £ pulses were recorded, ev^nt by event, on a paper tape

by means of a 3 parameter data acquisition system for detailed

o f f - i i na analysis with a computer. The coincident & L and L pui3ua

uijre altso fed to a Particle Identi f ier (^'1) uni t , fabricated by

Electronics Oii/ision, BrtRu, Jnd thu PI output uus recurded in a MC/t.

The enarjy spictrum ( A t + E output) uas fed to another FICn which

was r luted, by the t r i tun Jnd alphd pdrt icla PI pulses, into the

two haluas of the I1CA, Fissiun a^ well as LCP—fiosion

-47-

uitre monltorad and the maasuramunts nitre carried out at incident

neutron energies of 12U, 23u and &00 keV and the latter were

yBneratud by Li(jJ,n) Ba and T(p,n) He reactions U3ing the 2 Hal/

I/an de Graaff accelerator at 11T, Kanpur. Each of thBse fast neutron

runs was precodud by a thermal neutron run which was carriud out by

thermaliziny the Fast neutron beam.

Fig.?.$ shows the particle identifier [(it + £) XtJ specLra

•rifr120 KeV

TRITONSLRA

THERMAL

eo

40 >Z

<

ao or

10 14" 6 10 U

E:NERGY IN MeV22 26

Fig,7.1. Total energy spectra corrected fo*- tnetgy loss.

Qbsurued in 12u ks»U and thermal neutron fission runs, where the

alpha particle peak is seen to be separated fro.ii tha triton and

proton peaks. Fit}.7.1 shows the inargy (A£ + £> spectra in these

two cases, corrected for the tneryy loss in ths Source, gas and

aluminium anode foil. Preliminary results indicate that triton

yield in fast neutron fission increases substantially ( ~ 200^)

compared to that in thermal fission, whureas the change in anargy

-48-

spectra is not so striking. Further work on this project ie in

proyruas.

24, ,60

"hP T

. v.

Cfl 8

I*O

= 120 KeVALPHAS

•• r i L..-.X.-I i-**•'

« -

i= THERMALALPHAS

-.- I .- - . ,

40 80 240 280 320

A E x E CHANNEL NUMBER

Fig.7.2. Particle Identifier apactra

40

20

0

40

20

0360

• Indian I n s t i t u t e uf Technoloijy, Kanpur.

NUCLEAR PHYSICS

-49-

NUCLEAR PHYSICS

The research programme at the Van de Graaff laboratory

includes Nuclear Reactions and Nuclear Structure Studies

(both experimental and theoretical) as well as use of ion

beam techniques for applied research.

The experimental programmes have centered around (p,n),

(ptt") and (o(,oO studies. Considerable effort has been

devoted to the theoretical studies for nuclear induced

reactions ae a part of our interest in the Nuclear Data

Programmes. Nuclear Structure, Pion reaction, (p,2p) and

other knock out phenomena, ion-ion potentials and heavy

ion collisions are other areas where theoretical offer has

been directed.

Production of Burface alloys by ion implantation and

blistering studies by helium ion bombardment of metal

surfaces have been carried out in the area of applied

research with ion beam techniques.

-50-

1• Real and imaginary parta of the nucleus - nucleusinteraction using a microBcoplc approach. (tJ.K.. Guptaand S. FaTIas)

The energy density formalism is extended into thecomplex domain to calculate both the real and lmapirmryparts of the ion-ion potential. Recent nucleon-nucleuBpotentials calculated by Jeukenne, Lejeune and Mahauxusing Reid's hard core nucleon-nuoleon interaction areemployed to generate the complex potential energy densities

required in the calculation. The computed potentials are• 2)in good agreement with the phenomenologieal values '. The

computation of eilastic scattering crosr sections foridentical lone is in progress.

1) J.P. Jsukenre, A. Lejeune and 0. Mahaux, Phys. Rev. 0)680 (1977)

2) 3.K. Gupta and S. Kailas, Phys. Letts. 2l§, 398 (1978)

2. Volume inte^yals of nucleon-nucleus optical potentials."nmailas a.nd S.K. Gupta)

Volume Integrals of both the real ' and imaginary ' partsof nucleon (n ard p) nucleus optical potential are computedusing the existing phenomenological analysis for A = 10-238.These results are in good accord with the Jeukenne-Lejeune-Mahaux (JIM) rajdel'' which employs Reid's hard core nucleon-nucleon interaction. The integrals for neutrons and protonsare also fittel with an empirical expression

where t = 1 for protons and -1 for neutrons. *X and J~tare the coefficients of isoscalar and isovector componentsof the volume integral. The second part of the expressionrepresents the effect of volume and surface form factors

of the pott ivtlal and K i;< thu ra^lo of their strengths.The above expresaion describes the volume Integral data ofprotons and neutrons adequately.

1) S. Kallaa and 3.K. Gupta, Phys. Rev. £T£, 2236 (1978)2) 3. Kaila8 and S.K.. Gupta, Phys. Letts. JJLB, 271 (1977)3) J.P. Jeukenne, A. Lejeune and C. Mahaux, Phys. Rev. C16

80 (1977).

3. Comparison of nucleon scattering cross aections withfoie JLM microscopic optical model. (S. Kailaa andS.K. Gupta).

In analysing the nucleon-nucleus scattering data, it iecustomary to use phenomenological optical potentials and varythem suitably to best fit the experimental data. However,this approach suffers due to ambiguities in the potentialsets determined phenomenologically. A better approach willbe to predict the nucleon-nucleus potentials from a micros-copic calculation starting from nucleon-nucleon scatteringdata and use them in the cross section calculation. An attemptin this direction has been made by introducing the JLM micros-copic nucleon-nucleus optical potentials ' in a conventionaloptical model programme ' and calculating the elastic eoatter-ing cross sections for a large number of nuclides for a rangeof nucleon energies. These microscopic potentials in general,predict cross sections which are in reasonable agreement withthe experimental data. However, some refinements of thevarious potentials are needed to best fit the data.

1) J.P. Jeukenne, A. Lejeune and C. Mahaux, Phys. Rev. C16.80 (1977).

2) T.P. Viyogi and N.E. Ganguly, BARO-I-361.

-b2-

4. Fluctuation analysis of Ca(p.n) 3c total excitationfunction from 1.9 to"5*TT MeY. (Gulzar Singh*. S. Kailaa.A. Chatterjee, S. Saini, M. Balakrishnan and M.K. Mehta).

The total excitation for the Ca(p,n)*8Sc reaction

measured earlier ' has been subjected to detailed fluctuation

analysis. The peak counting, Fourier analysis and the

auto correlation methods have been used to extract the

coherence width C and it is determined to be ^ 6 keV.

This has been used to obtain the level density parameter a.

a = 5.48 MeV . The excitation function variance (C(o)) aa

well aa cross section probability distribution indicated

an insignificant direct reaction contribution.

• DAB Research Fellow, Pinjab University.

1) Gulzar Singh et al, NP & SSP 3ymp. \ofB, 29 (1976).

5. Calculation of (n.2n) cross sections around 14.5 MeVusing an integrated preequilibrium-cum-statistical model.(A. Chatterjoe and S.K. Gupta).

The absolute values of the cross sections for the (n,2n)

reaction around 14.5 MeV for nuclei throughout the periodic

table have been calculated using an integrated preequilibrium-

•cum-Btatistlcal model approach. The preequilibrium component

is calculated using the Griffin-Williams ' exciton model

employing the global value of the parameter occurring therein

as determined by Braga-Marcazzan et al ' for (n,p) reactions.

In Fig.5.1(a) the results are compared with the experimental

cross sections as compiled by Kondaiab/^. The calculations

are in good agreement with the data for the heavier nuclei

but for low A and small excess residual energy, \J-n- E h~ S h >

they are discrepant. In Figs. 5.1(b) and 5.1(c), it is seen

-53-

that the histogram of <T t I °~^he0 peaks at 1.0 forthe present model Instead of 0.8 for the purs statistical-equilibrium (EQ) model.

CROSS SECTIONS FOR IME <n,2n> REACTION « I I t 5 >

USING PC - EO MODEL.

Fig. 5.1. Cross Sections for the (n,2n)Reaction at 14.5 MeV using PE-EQ Model.

1) J.J. Griffin, Phys. Rev. Lett. JJ, 478 (1966).2) G.M. Bragga-Marcazzan et al, Phys. Rev. £6, 1598 (1972)3) E. Kondaiah, J. Phys. A7, 1457 (1974)

6. Resonance spectroscopy of the nucleus _Ti.(A. Chatterjee, S. Saini, 3. Zailas, H. Balakrishnanand H.E. Hehta).

The levels in the Ti nrileus in the excitation energyrange from 7.8 to 9.5 MeV have been studied by means of the

Ca (c<,c<) Ca reaction. The excitation function for thisreaction has been taken at the four laboratory angles: 84°,120°, 137° and 165° for J MeV < E^ < 4.75 MeV. Many anomaliesare observed in the excitation function and some of these

1 2)correlate well with resonances which have been seen ' ' Inthe 40Ca (o<, Y)44Ti reaction. A multilevel R-matrix

-54-

analysis to extract the spins and parities of the popu-lated levels is underway.

1) W.R. JHxon et al., Phys. Rev. £1jj, 1896 (1977).2) J.J. Simpson et al., Phys. Rev. C4, 44? (1971)

7. Nuclear structure of scandium isotopes (S. Saini andM.R. Gunye*).

A large amount of experimental data is now availableon the pf-shell nuclei with the advent of heavy-ion inducedreactions in recent years. This has revived the interestin the studies of the structure of these nuclei. The earlytheoretical investigations on the structure of the pf-shellnuclei were carried out in the framework of spherical ' andthe phenomenological deformed rotation-particle-coriolis-coupling (RPC) model '. The restricted shell model calcu-lations in a pure ( f" y/3 ) configuration were able to accountfor a large amount of the then available experimental dataon many pf-shell nuclei. It is, however, quite obvious thatthe static and dynamic properties of many of the observednuclear states can not be described in terms of such restri-cted shell model calculations. The recent studies'**' withthe extension of the shell model space to include completepf-shell, have led to a significant improvement in correlatingthe observed properties of Ca isotopes and the isotopes ofSc and Ti with A ^ 44. Such exact shell model calculationsin the configuration space of the full pf-shell are notfeasible for heavier elements with A y- 44, because of theformidably large matrices that are to be diagonalised.However, in view of the substantial pile-up of the experi-mental data, particularly on high spin states populated inheavy ion reactions, it is worthwhile to make t. systematicstudy of these nuclei employing a realistic nucleon-nucleon(KN)

-S5-

interaction in a large configuration space of the

complete pf-shell. The high spin states have probably a

simpler nature and their study may provide a significant

insight into the intrinsic nuclear structure.

The present calculations for scandium isotopes

(A = 44-48) are performed in the framework of Hartree-Fock(HF)

projection-^ formalism employing the Kuo-Brown ' effective UN

interaction modified by Mcffrory '. The calculations were

also done by using a slightly different version of the modi-

fied Kuo-Brown NN interaction '. An inert Ca core is assumed

and the single particle orbitals f7y , p3, , f . and

D|/ are included in the active space. The single particle

energies of these basis states are taken from the observed

spectrum of Ca. The HF calculations with axially symmetric

deformations show that there are many energetically close

Intrinsic states of the scandium isotopes. This necessitates

a band-mixing calculation ' to determine the admixture of

various close-lying intrinsic states in the computed nuclear

wave functions. The nuclear wave functions obtained from

the lowest six HF intrinsic states by band-mixing prescription

were used to extract nuclear energy levels, static electric

quadrupole and magnetic dipole moments, and the electromagnetic

transition probabilities. The calculated and the experi-

mental *°' energy spectrum for Sc is displayed in Fig. 7.1.

The low-lying negative parity states in this nucleus are very

well explained by the present calculations. The electric

quadrupole moments and the B(E2) values were calculated using

the effective charges g.p = 1.33« for protons and en = O.64e

for neutrons. The experimental calculated electromagnetic

properties of the low-lying negative parity yrast states are

compared In Table 7.1.

-56-

Table 7.1

The static moments for the ground state

P-calc^ S-SL1U- {Mobs = 5 3*

The B(B2) and B(M1) for Y-transitionsbetween the negative parity yrast statesin 47sc are listed below:

J i

3 /2

5/2

5/2

11/2

9/2

9/2

9/2

15/215/2

13/2

i3/2

1/2

J f

7/2

3 /2

7 /2

7/2

5/2

11/2

7/2

11/215/2

9/2

11/2

3/2

B(B2, J± -^

Expt r e f '8>

292.2

-4551 - 6 1 1! ! 6 ? 5

109.4 ± 30.9

<25544

2.02 - 1075.0

2 # 6 2 - 2!42

< 272<2458

<2901

O A

Jf) e. fm*

Caic.

91.32

41.48

3.55

44.34

38.59

3 . 7

15.66

21.7633.00

17.81

4.96

79.7

Bxptr<jf'8)

0n43 + 0.34

0.17 + 0.10

0.39 + 0.23

0.043 ±0.025

0.29 -2.92

0.054

Calc,

1.78

1.50

2.21

0.49

4.41

0.30

0.43

* Member of Theoretical Reactor Physics Section

- 5 7 -

5a.Ui

z

u 2

7

19

EXPT CALC. SM

fig. 7 .1 . Energy Spectrum of

1) J. McCullen, B. Bayman and L. Zurmick, Phys. Rev. 134.B515 (1964)

2) F.B. Malik and W. Scholz, Phys. Rev. 150, 919 (1966),Phys. ttev. 152, 1071 (1967)

3) J.B. McGrory, B.H. Wildenthal and B.C. Halbert, PhyB. Rev.C2, 186 (1970)

4) J.B. McGrory, Phys. Rev. C8, 693 (1973)

5) C S . WsiTke and M.R. Gunye, Phys. Rev. V&, 1084 (1967)

6) T.T.S.Kuo and O.B. Brown, Nucl. Phys. A114.S41 (1968)

7) 3. Saini and M.R. Gunye, J. Phys. G.4 to appear inJ. Phys. G.

-bB-

8) M. toulemonde, L. Deschenes, A. Jamshidi and N. Schulz,Nucl. Phys. A227. 309 (1974), ibid, 325 (1974)

9) J.M. Delbrouek - Habaser, Y. Baudinet - Robinot andJ. Vervier, Nucl. Phys. A227, 257 (1974)

8. Direct and collective nucleon-capture. using micros-copic optical potential. (D.R. Chakrabarty and 3.K. Qupta),

The fast nucleon capture essentially takes place through

direct and collective processes. In the collective process,

the projectile excites the target to the Giant Dipole State

(GDS), itself falling into a bound orbital. The core de-

excites to the ground state by &.f(\. de-excitation.

The particle-vibration coupling, responsible for the exci-

tation of the target depends on the iso-vector part of the

nucieon-nucleus optical potential. Jeukenne, Lejeune and

Mah..u>: (JLM) have calculated ' recently, the total optical

potential along with the complex iso-vector component, from

a microscopic approach starting from Reied's two body inter-

est 'on. The capture cross-section data, demand to be a

testing ground for the potential. We have calculated the

capture cross-section usiag the microscopic potential for

the case 208Pb(n, </).

2)The form of the particle vibration coupling is '

H

where oC is the operator exciting the GDS, \ZI(TJ is the

optical potential

and the capture cross-section from the initial continuum

state \l'l'\to the final bound state I If}' i s

, 1000U

15 11

En(MeV)10

IT

Fig. a.1. Experimental and Theoretical Capture CrossSection to different states in 2°9pb.

-6U-

where D and I are radial Integrals. D describes the direct

capture and I, the collective capture and contains in the

integrand Vi(r) and a constant relating to the sum rule

limit.

Potokar" , for fitting the experimental data, found

that Vj(r) should be made complex. The calculation by JLM

predicts the complex isovector part. We have applied their

prescription to calculate Vi(r) and the total optical208

potential for neutron on Pb and the continuum wave func-

tions were generated from that. B.3. wave functions were

calculated from a real WS potential.

The results of our calculation is shown in the figure 8.1,

The agreement, though not ^ood, can be considered reasonable,

aince effectively there was no adjustable parameter in the

whole calculation. However, the disagreement may of course

point towards some imperfection in the microscopic potential

calculation.

1) J.P. Jeukenne. A. Lejeune and C. flahaux, Phys. Rev.£!£, 80 (1977).

?) G. Longo and F. Saporeffi, Nucl. Phys. A199. 550 (1973)

3) M. Potok-ir, Pbys. Lett. 46B, 346 (1973)

9- 19F(ol,n)22Na reaction (M. Balakrishnan, S. Kailas andM.K. Mehta).

From the excitation function obtained in the 9F(o<fn)22

Na reaction, eight well resolved resonances have been

analysed for the various resonance parameters. A detailed

paper including strength function analysis has been prepared

for publication.

-61-

10. Level scheme of 81Rr( Y.K. Agarwal*, G.V.K. Baba,S.M. Bharathi*, V.M. Datar, H.C. Jain* and B. Lal+)

Q * R 1

The level scheine of Kr was studied through the Br

(p,n) reaction with the 5.5 MV Van de Graaff accelerator.

•/* -ray excitation functions, V- V coincidences and convers-

ion coefficients of some low lying transitions measured

earlier were U3ed for this purpose. New levels were proposed

including a level at 50 keV associated the a . neutron

orbital. The half life of this state was measured taking

coincidences between neutrons feeding that level and the

50 keV gamma. An n- V*discriminator employing a NE 215

liquid scintillator was used to cut the gamma background in

the neutron detector. The half life was found to be 4.0 +

0.4 n sec.

Tata Institute of Fundamental Research, Bombay 400 005

Multi Disciplinary Research Scheme, BARC, Bombay 400 085.

11. Search for bound polyneutron nuclei in the fission of J U(C./.K. Baba, V.M. Datar, V.K. Bhargava*, R.H. Iyer *,S.G. Marathe* and V.K. Rao*)

There have been several attempts ' to detect a particle-

bound polyneutron system *V\ with x = 2-4. Recently Detraz '8 6

has reported evidence for the production of n or n in a

24 GeV proton interaction with tungsten. During the course of

the present work Turkevich et al^' reported a negative result

for the production of n in a 700 MeV proton interaction

with uranium.

Since in thermal fission of U several neutron rich

nuclei like He are produced, polyneutron nuclei, if they exist,

can also be expected. The present work reports on a search

for a bound palyneutron nucleus in fission.

-62-

Thia search has been made with two probes viz. Rb andPb. In the first experiment upto 12 gma. of purified RbNO,,wrapped in a 0.3 mm thick Cd absorber, was irradiated forperiods of upto 9 hrs. near the core of tne reactor APSARA.91 92 6 8J • Rb is expected to be produced by ' n through xn react-ions. The 91'92Sr activities (Ty2 = 9.67 hrs. and 2.71 hrs.respectively) were radiochemically separated and counted

nt noin beta-gamma coincidence. There was no y'f* Sr activitydetected above the background counting rate of 3/hr. Assuming

91 92a cross section for the production of 3 I»* Rb of 100 mb,an upper limit of 10"'/fission for the yield of ' n couldbe placed for the production of these neutral nuclei.

In the second experiment upto 12 gms of pure Pb(N0,)2 w e r e

irradiated and the Bi activities which are expected to be212 21 "*>formed due to the decay of *•"•* '-'pb were radiochemically

212 213separated and counted for the alpha-decay of ' Bi witha surface barrier detector. No counts above the backgroundrate of 1 count/hr could be seen and here again an upperlimit of 2 x 10" /fission could be placed for the productionof ' n, assuming a cross section of 200 mb for the produ-ction of 2 1 2' 2 1 3Pb.

Thus it is concluded that if bound polyneutron nucleiexist, they are not emitted in thermal fission of U witha yield of more than 2 x 10 /fission.

* Radiochemistry Division, BAHC1) 3. Fierman, S.S. Hanna, Nucl. Phys. A251. 1 (1975)2) 0. Detraz, Phya. Lett. 66B, 333 (1977)3) A. Turkevich et al., Phys. Rev. Lett. 2§, 1129 (1977)

- b l i -

12, A method of alternate recording of ON and OFF resonanceV-spectra at a last rate. (D.R. Chakrabarty, H.H. Ozaand N.L. RagoowansiT-

induced capture resonance study is met with

a neutron induced background spoiling the spectruw upto 7 to

8 MeV. The carbon build up, which is the source of the neutrons,

may introduce a systematic unestimable error if we measure

the yield of ^ 8 MeV resonant '/-ray by taking very long run

ON resonance Bpectrum and then very long run OFF resonance

spectrum. This error can be reduced by recording the spectra

alternately at a fast rate.

The circuit, we are going to describe, essentially does

thia job. After collecting say ON resonance spectrum in one

part of the memory of MCA for a specified CI. Counts, the

magnetic field of the analysing magnet of the Van de Graaff

accelerator, at once changes to a value corresponding to the

OFF resonance beam energy. However the magnet takes some

time X^ t to settle to OFF resonance value and both the

C.I. sclar and MCA are inhibitted for this time tfl, after

which other part of the memory starts collecting OFF reso-

nance spectrum and the cycle repeats.

Fig. 12.1 describes the circuit. At the end of pre-

assigned counts, C.I. scalar gives out a square wave, the

falling edge of which triggers the negative edge sensor

circuit which produces a spike which in turn triggers a

timer whose output is another square wave of controllab]s

width tfl. The spike also triggers a flip flop FF1 which

switches on or switches off a definite current A I into the

magnet coil to provide ON or OFF resonance conditions.

The inverted output of the timer inhibits counting in C.I.

scalar for time t^. The complimentary outputs of flip

flop FF2 triggered by falling edge of timer output are

combined through AND-gatss to inverted timer outputs to

-64-

Fig.12.1. Circuit diagram for generat-ing different timing pulses.

v* ttigttens 01

FF2(0)

FF2(8l

ROUTER1

ROUTER2

i-0

OUTPUTS FROM VARIOUS GATES

Fig.12.2. Timing sequence of the pulses.

-65-

derive gating pulaea fed to the router 1 and ? of the MCA.

Fig. 12.2 tells us thus, that when FF1(Q) and so the

magnet current changes, both H1 and R2 are 0 for time t<j and

then either R1 or R2 goos to state 1 alternately. This means

that MCA remains inhibitted for time tfl after magnet current

changes and then alternately two parts of the memory collect

data depending on whether beam energy is of ON or OFF resona-

nce value.

13. atrong absorption model for plon Induced knock-outreactions. (B.K. Jain and S.C. Phatak*)

A strong absorption model for pion-induced knockout

reaction is proposed. The distortion of the incoming and

outgoing pions has been included by (i) computing the pion

wave number in the nuclear medium (dispersive effect) through

dispersion relation and (ii) excluding the central region

of the nucleus where the real pion absorption is dominant.

Various approximations used in the impulse approximation

theories are examined. The theoretical results are compared

with experimental data. The agreement between the theoretical

results for separable off-shell extrapolation and the data

is good.

(published in Nucl. Phys. AJ02, 401 (1978) )

* CSIR Pool Officer

14. Off shell effects in (TT"*.' ]f"V) reaction on 1 20.(S.C. Phatak* and B.K. Jain).

Several experiments have been done for (TT , ~ITN) react-

ions. In the theoretical analysis of these reactions,

normally the "impulse approximation" framework is used,

vhere the cross-section is written as

7 ^ J - k'« J

Here F. . is the kinematic factor, P(Q) is the momentumkin • *Z£ . tsW/distribution of the nucleon in the nucleus and <Xcr

is the free TfN cross-section. In the knock-out formalism

the off-shell TTN t-matrix is required. The factorized form

appearing in eq. (1) is valid only if off-shell effects are

not important. In proton - induced knock-out reactions this

probably is true aince the energy-variation of the free

nucleon-nuoleon cross-section is small. Howover in case of

( It , TTN) reactions in the 3-3 resonance region, these off-

ahell effects could be very important. For the investiga-

tion of this point vre have used the framework of strong absor-

ption model, where it is assumed that the knockout process

takes place on the surface of the nucleus. Inside the nucleus

mainly the absorption (real) of pion occurs. The radius of

this strongly absorbing sphere is giver, by "ft" R (B^) = <3^bs(E-,,- ). Based on this idea the transition amplitude ia given

r>where 0. = (1 - A" ), Q is the momentum of the recoiling nucleus,

N is the wave function of the bound nucleon and L-rtf is

the off-shell TT — N scattering matrix. In terms of th9

asymptotic momentum of the outgoing protons (KN ) and the

32

24

1"5 16

b

. Klssllngtr_ _ . Scparibl«(n.3.6fnT')

. . S«parabl«(LMM)» _ _ On »h«ll

40 10 120 160

4.0

abK (»• l.t lm~')

. S.tpanblt (8 . 3.6 tnT'). . Separable (LMM)

o

I

Fig.14.1. Angular distribution of protons Fig.14.2. Energy spectrum of protoia

-66-

local momenta of the incoming ( K ,r) and outgoing (K^) piona,

the relative momenta \t_ are given as

The local plon momenta K _ (K ) are determined from the dis-

persion relation,

fa)where P , C and f are the asymptotic momentum, nuclear density

and the TT N forward scattering amplitude, respectively. The

best choice for E seems to be

C5)where r, f.c f ^/^ are the lab. momenta of incident plon,

cattertd pion and nucleon, respectively. Eg is the binding

energy of the knocked out nucleon in the nucleus. For the T

ooth 3 and P-waves have been included. The off-shell part

of the 7T-N t-matrix is parametrized as

The off-shell form factor ^ is chosen to be l//kj= K Ik *•*•/•<) ~'

for P-wave and \f (K) = (K2 + p2) for $ -wave.

The numerical results for the energy spectrum of protons

:.nd the angular disxribution of pions are shown in Pigs.

14.1 and 14.2 at 112 MeV of incident energy. Two curves

correspond to fi = 1.8 fm and 3.6 fm . Other two curves

are for the Kisslinger form ' and the multichannel separable

-69-

2)model of l.onder,j«n et al. ' We have also plotted resultscorresponding to the on-shell factorized prescription (eq.1).These figures clearly show that the results are quite sensi-tive to the oft'-shell form. The use of factorized on-shellvalue Beeras to underestimate the cross-section.

* CSIR Pool Officer1) L.3. Kisslinger, Phys. Rev. £8, 761 (1955)2) O.T. Londergan and B.J. Moniz, Phys. Lett. 45 B. 195 (1973).

15. Scrutiny of the impulse approximation for (p.2p) reaction(B.K. Jain)

The co-planar symeetric (p,2p) reaction is widely usedfor the study of single particle aspect of the nucleus. Inthese studies impulse approximation 1B used to extract theinformation from the experimental data. Since this approxi-mation seems to be valid above 100 MeV in the elastic scatter-ing, same region of validity is thought to hold for the co-planar symmetric (p,2p) reaction. However, due to the factthat the latter reaction differs from the elastic scatteringin momentum transfer and the form factor, the validity of theimpulse approximation requires examination for the knock-outreaction. Following the KMT approach, we have studied thecorrection for * 0 in the region 100-300 MeV for Is and Upknocked out protons. The results are shown in Figs. 15.1 and15-2. From them it may inferred that for low binding energy(r^ 10 MeV) protons the correction is negligible above 200 MeV,while for high binding energy ( 4 0 MeV) protons it isnegligible above 250 MeV. Below these energies the impulseapproximation results could be as big an overestimate as afactor of 1.5.

1) A.K. Kerman, H. McManus and R.M. Thaler, Ann.Phys. 8,551 (1959).

I Transition Matrix | 2 { ret. units)

O

P>

o3!(0

1

1

1

/

/

^ ^ i -

c

1

' 1

I//

/11

* =•o

1 11 "

1

' //

1

11f1

- oo

- %

I

mn

Eno

(D

O

X)

-Q

VI1

oo

0<J

ro

•a

K)

Oo

[Transition Matrix | z ( re|. units)

O

-71-

16. Nuclear friction and the imaginary part of the nucleus-nucleus Interaction potential (Bikash Sinha)

Using semi-classical approximations, the phenomenolo-

gical form-factor of nuclear friction is derived from the

imaginary part of the nucleus-nucleus interaction potential.

The results obtained for the friction co-efficient a^ree

well with experimental data on damped collision for two

nuclei.

17. Average nucleon-energy excitation and energy dissipationin heavy-ion collision (S.C. Phatak* and Bikash Sinha)

The average energy of excitation of a nucleon for two

colliding nuclei has been computed ut-ing plane wave inter-

mediate states. The classical co-efficient of friction has

been estimated in terms of the imaginary part of the optical

potential.

* CSIR Pool Officer

18. The imaginary part of the nucleus-nucleus opticalpotential ( S.C. Phatak* and Bikash Sinha )

The contribution to the imaginary nucleus-nucleus

optical potential has estimated by evaluating the energy-

conserving second-order term in the perturbation series.

The incoming nuclear field is supposed to excite nucleons in

a nucleus in this calculation and the nuclear excitations are

approximated by particle-hole excitations in a Fermi gas.

The resulting imaginary potential compares favourably with

phenomenological potentials.

• CSIfi Pool Officer

-72-

19. The nucleus-nucleus interaction potential using density-dependent delta interaction (B.Sinha and S.A.Moszkowski)*

The interaction potential between two nuclei has been

calculated by using a generalised folding model. The direct

and the exchange terms are computed by folding in Skyrme

interaction with the nuclear density distributions and the

density matrices of the two nuclei respectively. A new defi-

nition of the one-body optical potential is also suggested.

The results agree quite well with standard phenomenology.

20. Nuclear structure calculations using momentum-dependentdelta interactions (MDD) (Blkash Sinha and Steven A.Moszkowski*)

The ground-state properties of a nucleus have been in-

vestigated using momentum and density-dependent £ inter-

actions. Unlike Skyrme type of interaction, the two-body

interaction used has terms dependent on the fourth power of

the relative momenta. The role of these new terms has been

investigated by using the density-matrix expansion techniqutt

of Negele and Vautherin. The interaction has been used to

calculate, amongst other phenomena, the ion-ion interaction

potential and the nucleon-nucleus optical potential. The

improvements obtained using such an interaction over Skyrme

type of interactions have been discussed in detail. It is

shown that the effeotive mass, m*, is larger in magnitude than

obtained by using Skyrme type of interaction, whereas the

modulus of compression is 240 MeV rather than the usually

large value obtained by using Skyrme interaction. It has

been suggested that such interactions could be more appropr-

iate than Skyrme type of interactions in physical situations

where large momentum transfers are involved.-

* University of California, Los Angeles, California 90024,USA

-73-

21 • Mi(,*roBc;opjc •:&lcu3at,1on of D-o< scattering with 6-bodyan'tTtajfumetrfz'ed' wave function (Kiran Kumar* and A.K.Jain)

A Born approximation description of medium energy D-e(

scattering uaing N-oC potentials of any of the Gaussian or

Saxon Wood's form has been shown to be inadequate in our

earlier calculations. The same type of Born approximation

treatment has however been proved to work very well for p-d

scattering. In order to understand the discrepancies in

uaing Born approximation for the d-o<. scattering, this micro-

Bcopic calculation has been done. In these calculations fully

antisymmetrized 6-particle wave function has been used along

with a Serber type N-N interaction. In order to simplify

the calculations the Yukawa form of the N-If potential has

been expanded in terms of a series of Gaussians. The matrix

element for the d-oC scattering is written as

Jwhere the 6-particle antisymmetrized wave function L~j

is written in terms of unantisymmetrized wave function jr

(1234}56) has been expressed as a product of internal

wave functions of oc and d and a plane wave d- o£ relative

wave function

-74-

Uaing these wave functions and interaction the final matrix

element reduces to the evaluation direct (DIR), single

exchange (SE) and double exchange (DE) termb.

These terma as derived for m = 1 are for example:

t-

(I) X

The integrals IDjo» XfZ etc. have been evaluated to

obtain the d + <x. scattering cross sections. For example

such that £U , lf-k\ r - f ^ A fis= /8(.Elwith Bi end A ^ representing the Gaussian expansion coeffi- '

cients of Yukawa form.

Finally the differential cross section can be repre-

sented as

A^ _ /d /^, Y, IH /*

10

20 40 60 80 100 120 140 160

10 =

10

-SHRUNK DEUTERONRADIUS • 1.1 fm

• DEUTERON RADIOS- 3 Ofm

ALPHA PARAMETER

» -0.5l4fin"2

- ALPHA PARAMETER

<* •0.44fm"2

(ALPHA BROADENED)

• ' ' L__i_20 40 60 30 100 120 140 160

9 . -

I

I

Fig. 21.1. Angular Distributionof D-2 Scattering with MicroscopicCalculation at 34.7 MeV.

Pig. 21.2. affect of Alpha and DeuteronStructure on Angular Distribution

-76-

Fi^. 21.1 shows a comparison of these calculations

with the experimental data. As ia evident the maxima and

minima have not been reproduced in these calculations also.

This indicates that one can not use the Born approximation

anl the trouble in this analysis arises aB a result of

large distortions in the relative c<. +d wave function, it

thould no longer be taken as plane. A further analysis

of the exchange terms indicates that the direct term is

most dominant, the single exchange term affects the matrix

element significantly while the double exchange term con-

tributes negligibly (eg. at 9cm = 5°, I g B is 3 times smaller

than I D I R while I D E is ~25OO Bmaller than IDE)« This

indicates the possibility of analysing the d+oc scattering

in terms of resonating N +oL and P +oC structures. This

Its supported by the fact that (see Fig. 21.2) the size of o<:

does not have much influence on the angular distribution

while the d size has enormous influence on this. Thus

even the oL -distortion or size is changed during the scatter-

ing it does not influence the distribution. Thus a cal-

culation in which the gross features of Yl-oi Interaction

are properly accounted for should reproduce the d-o<

scattering.

• NUMAC, fiadiochemistry Division, BARC

-77-

22. Nuclear Exchange as a mechanism for strongly dampedheavy ion collisions. (A.K. Jain and N. Sarmal

There hive been several attempts to explain the large

energy transfer to internal degrees of freedom in terms of

frictional forces between two liquid drops. All these

resulted in a meagre '" 20 MeV transfer to internal excita-

tion, i.e. very small as compared to experimentally observed

values of the order of ^100 MeV or more. The data is

characteristic of a process of very short duration of the

order of 10~ sec. also. We regard the scattering in a

semiclasaical approximation as the collision of two clouds

of nucleona. The momentum distribution of the nucleons in

each nucleus is determined from experimental nucleon density

distributions in the Thomas Fermi model.

During the interaction of the two heavy ions, nucleons

diffuse across the surface between the nuclei. Nucleon

transfer leads, because of the velocity mismatch, to a

change in the momenta of both nuclei and brakes their relative

motion. It Tollows from kinetic theory that the number of

particles crossing unit area per unit time is f fr'J^/b. -

at any point f for nucleons with speed u and density <f /rJ

The rate of change of momenta of nucleus 1 (see Fig. 22.1)

due to nucleon transfer from it is

A similar expression is obtained for . ? . The loss in

kinetic energy occurs all along the trajectory as determined

by the Coulomb and nuclear potential. The total kinetic

energy loss E* appearing as the internal excitation of the

-78-

nuclei is consequently

wliere /^M is the net nucleons transferred from 1 to 2.

Computations based on the above formalism were made on

several reactions. For these cases the angle of inelastic

scattering in centre of mass, 0 , the energy loss, E*,c • in*

the nett number of nucleons transferred A M = A M, — Zi fV|„

and the total mass exchanged between the nuclei AM-j-&fVl2were calculated as a function of the impact parameter b.

A typical example of 84Kr + 209Bi at 600 MeV is given

in Fig. 22.2. Attractive nuclear potential induces a certain

orbiting resulting in a sudden dip in ©„ „ curve. At thist C * ID.*

b the total mass exchange abruptly rises and B* increases

rapidly. The differential cross section for scattering in

the classical limit is

For the example in Fig. 22.2 the computations show a small

anomaly in the slope of the 9 curve which gives a peakC . ID*

in the deep inelastic angular distribution. The peak cross

Bection for the 84Kr + 209Bi at 600 MeV is estimated to be

~ 400 mb/vr , which compares well with the experimental value

of 575 mb/sr.

-79-

This aemielassical model reproduces the basic featuresof the strongly damped collision of heavy ions, i.e. the largeenergy transfer to internal excitation but timall mass transferto the projectile, and qualitatively the very anlsotropicreaction cross section. The duration of the damping process

—21is estimated to be extremely short, around 10 sec.

Fig.22.1.Rate of change of momentadue to nucleon transfer

I 6 •

aa.

E

-10 "5 10

10

20

20 301 ;

i :

* ' • 8

- .

40

—,

.AM, -t

60

iO

AM,

,AM,H\.

M2

BOI

50

^AM 2

209B , "

) McV

Xs

-

mo E*|20 40 60 BC 100 9'cl

Fig.22.2. 74Kr + 209Bi at 600 MeV

-80-

23. Empirical rulea for substltutionality In metastablesurface alloyg proituced by ioa implantation(D.K. 'oood)

1 2)

Metastable surface alloys are produced ' ' by ion im-

plantation at/below room temperature in most metals. At

these temperatures, atomic diffusion is negligible and thus

normal solubility limits can be exceeded. Surface alloys

of even immiscible species have been observed "•''. Ion

implantation could produce a vide variety of new surface

alloys (with important applications) of any atomic species

with any substrate in the periodic table. However, no

reliable criteria exist for predicting the most important

parameter - the substitutionality of a given implanted

specie:.!. Based on the extensive data now available on1 2)

substituticnality of several implanted alloys in copper ' '

and iron ', we propose empirical (modification of the Hume-

Hot.lery) rules for predicting substitutionality in dilute

metastable surface alloys 1 r-oduced by ion implantation.

Excellent agreement with published data on 63 implanted

alloys in i'e, Cu, Ni, V and Be establishes the general

validity of these rules. It is shown that the present

rules work much better for metastable implanted alloys

than the Home-Rothery rules do for equilibrium alloys.* to be published in Phys. Lett. A.

1) D.K. Sood and G. Dearnaley, in Applications of Ion Beamsto Materials. 1975. ed. 0. Carter, J.3. Colligon andST."A. Grant (Inst. Phys., London, 1976) p. 196.

2) J.A. Borders and J.M. Poate, Phys. Rev. Bj2 969 (1976).

}) D.K. Sood and G. Dearnaley, J. Vac. Sci. Teohnol. 12465 (1975). ~~

4) S.T. Picraux, in Hew Uses of Ion Accelsrators. e<±.J.F. Ziegler (Plenum Press, New York, 1975) p. 227

24. Ion Implanted surface alloys In nickel* (D.K. Soodand G. Deavnaley**)

Four surface alloys in nickel produced by hiph dose

implantation of Ta+, an+, Br+ and La+ ions are reported.

Rutherford backocattering and channeling of 2.9 MeV helium

ion beam in employed to determine the substitutional solid

solubilities and the radiation disorder. Ta, Jn and Er

form substitutional solid solutions beyond solubility limits

whereas La is found to be insoluble. It is shown that

these and the other implanted alloys reported ' in Nickel,

obey the reccit, 'modified Hume-Rothery rules' proposed by2)

Sood ' for dilute metastable alloys formed hy ion implan-

tation. The radiation disorder extends well beyond the

ranges of Sn+ and Er+ ions.

* to be published in Radiation Effects.

•*A.E.R.B., Harwell, 0X11 ORA (U.K.).

1) S.T. Picraux, in New Uses of Ion Accelerators, ed. J.F.Siegler (Plenum Press, New York, 1975) p. 22?.

2) D.K. Sood, Phys. Lett. A ( to be published).

25• Blistering by helium ion bombardment (D.K. Sood,M. Suncter laman* and R. Krishnan*).

Radiation blistering results in surface erosion of

structural materials during prolonged gaseous ion bombard-

ment. In this process ' the gas atoms get ifcplanted in near

surface regions, and if their solubility and diffusivity

are low, they rapidly agglomerate to form small gas bubbles.

With increasing ion dose, these bubbles grow in size and

when the internal gae pressure is high enough, they may

plastically deform the surface skin to form visible blis-

ters. As the irradiation is continued the blisters may

eventually repture exposing fresh surface for further exfo-

liation. This effect leads to serious 'first wall1 erosion

-82-

2)and plasma contamination ' during the operation of a

thermonuclear davice/reactor.

We have obtained some preliminary results on study

of blistering of Inconel-718, 316 S3, copper and zirconium.

Well annealed, electropolished specimens were bombarded at

about 10°C with 2 MeV helium beam. The ion flux was about

2.5 x 1015 Hw+ ions/cm2/sec at about 3 x 10~5 Torr. Total

do3e ranged from 0147 to 2.4 x 10 Tle+ ions/em . The

bombardment specimens were examined with a ETEC Scanning

Electron Microscope. All the four materials studied

exhibit blisters visible to naked eye.

* Metallurgy Division

1) O.M. Me Cracken, Rep. Prog. Phys. 28, 241 (1975)

2) R. Behrisch, Nuclear Fusion .12:, 695 (1972)

EXPERIMENTAL TECHNIQUES AND INSTRUMENTATION

-U3-

KJtPERIMKNTAL TEOllNl-jUKU AMU INSTKUMiiSTATION

1. Isotope oeparator i-S ctlon (V.A. Hattnngadl, F.R. BhathenaK.I.. PaTSTand" K. iJhnllom)

The assembly has been completed of one of the limbs ot

DUMAS mass separator and preliminary performance tests are

now under wiy.

The main magnet coils vere installed in position and

magnet performance tested during early part of the year. The

magnetic field has been found to vary linearly with the ener-

gising current upto a maximum of 10 KOauss without field

saturation. The field spatial distribution in the median

plane was.* determined using a Hall probe normalised against

a fixed NMH probe. The field has been found to be uniform

within +1.3 Gauss in 1 KG over the median plane region likely

to be covered by the ion beams. This is indicative of the

precision achieved in machining and assembly of the magnet.

The fringing fields at the entrance and exit pole edges were

also plotted and the Virtual Field Boundary was found to

conform very nearly with that assumed in design. The field

stability was also measured and found to be better than

+ 200 ppm.

The magnet chamber, previously dismantled for loading

the coils, was reassembled after the field mapping was

completed and proved vacuum tight once again. The ion source

and collector side vacuum chambers were then coupled on and

pumped down Co 10 Torr. The source limb has beer alighned

properly with respect to optical axis of the magnet. For the

initial performance tests, we have lined up only one of the

two limbs of the dual mass separator and an Argon ion beam

has been uaed for these tests. We get rbout 1 mA ion beam

current at the collector with ,~ood focussing of the image.

Further studies of the mass separator characteristics are in

progress.

-84-

2. Tandem Accelerator (M.G. Betigeri, T.P. David, P, Singh,i.JS. Soni, C.V. Rayarappan and M.K. Mehta)

Voltage Generator

The pressure vessel fabricated at the Central Workshops

was installed after teBte horizontally on the mountings in the

tandem shed. The end flanges were mounted on the trolley which

run on the rails laid on either side of the pressure vessel.

The support columns were bolted onto these flanges. Twr:

parallel running 76 mm gas pipe lines provided with valves

were run from the tank across the lawn and connected to the

gas storage system of the 5.5 MV accelerator. After closing

the flanges the terminal end of the column sections were conne-

cted by an aluminium cylinder for carrying out voltage tests.

The tank has been provided with a pressure gauge and an outlet

for cheoking the dew point. Voltage test was carried out

after pressuriting the tank to about 180 psi of dry insulating

gas (80£ N2 + 20 £ C02). The terminal voltage achieved at

this first trial monitored by the column current meters and

also by generating volmeter was 1.4 HV. Further increase of

voltage resulted in sparking at a couple of spark gaps which

was later found to be unevenly spaced. This was rectified

later.

The accelerating tube sections were araldited on to the

M.S. support tubes and mounted horizontally on the tank

flanges. These are provided with bellow sections (with stiffen-

ing rods) to facilitate alignment. The terminal ends of the

accelerating tubes have been connected up with the 6 mm dia.

bore stripper canal and 8 nos. of 12 mm dia.thrust rods which

when adjusted keep the tube under slight compression. The

stripper canal is provided with a thermocouple gauge head and

the gas inlet tube. The gas is fed through a needle valve

controlled by a perspez rod and its associated geared reversible

motor. The gas bottle filled with oxygen is mounted on one side

-85-

of the terminal column end plates. The terminal

cover was replaced by a stainless steel 630 mm x 600 mm

dia,polished shell, snugly fitted and screwed on the column

end plates using rounded aluminium ring.

The accelerating tubes are pumped from either side by

2000 (A oil diffusion pumps backed by a 800 ifa vapour

booster pump and a 450 l/m*n rotary pump.

With a vacuum reading of ^ 5.0 i to" torr outside the

tank flanges on either side and a tank pressure of ^ 1 8 0 psi

of dry insulating gas the terminal voltage reached was 1.7 Iff

during test. A pressure to vacuum leak detected in one of

the accelerating tube sections has been since located and

oorrected. Further test will be done after optimising the

negative ion output from the duo-plasmatron ion source now

under test.

Deflecting systems

Magnetic deflection system to enable shifting of the beam

parallel to the axis which consists of four electromagnets

has been set up along with an einzel lens to deflect the beam

in proper direction required for better focussing by accelera-

ting tube. + 20° analysing magnet is under'construction at

Central Workshops.

Ion optics

To perform experiments with any accelerating device it is

necessary to get a well focussed, intense and highly colli-

mated beam at the target which requires tracing of the ion

beam and therefore ion optics for the accelerating tubes of

2 MV Tandem accelerator was studied. Negatively charged

ions extracted from Duoplasmatrou source were injected into

the first accelerating tube. Since in the Tandem configura-

tion the beam has to pass through a small stripper, it is

imperative to know the conditions which produce a converging

-B6-

beam at the exit of the first tube. The space charge

being small the Laplace's equation y*V " 0 was solved

to obtain the potential distribution using an iterative

relaxation prooedure. For the boundary conditions two

different types of potential distributions have been taken

on the electrodes. Ion trajectories ware obtained by

solving the classical equations of motions of charge parti-

cles in the electrostatic field.

f - -*z

An arrangement with variable potential, gradient in

which the potential for the first few electrodes changes

slowly as compared to the rest of the tube was found to be

more satisfactory than the uniform potential gradients

arrangements to obtain convergent beam at the exit of the

first tube. For parallel beam the trajectories were found

to cross the z-axis at different points indicating some

spherical aberration of the extrance region. Using parabolio

ion trajectories in the second tube the radius of the beam

at the exit was found to be less than 1 mm. Those calcu-

lations indicated a decrease in the exit beam diameter for

beam with particles in higher charge states.

3. Ion Implantation (P.K. Bhattacharya, M.S. Bhatia,M.J. feansara, A.G. Wagh and N. Sarma)

100 keV Ion Implantation facility

A 100 keV ion implantation facility set up at Van de

Graaff laboratory has been completed and has been put In use

for fabrication of solid state devices, study of optical

integrated circuits and corrosion studies in metals. The

maximum terminal voltage obtained is 120 E7. All the terminal

-87-

supplies for ion source and associated circuits have beenconverted into tranaformer-less 3 phase supplies.

Filament auppl.y is SCR controlled 3 phase full wavebridge circuit giving 0-15Amps. D.C. output.

Extractor and focus supply are 10 KV and 15 KV regulatedD.C. supplied. Basically the circuit 1B D.C. to D.O. converter.The low D.C. voltage is converted into high frequency osci-llation, voltags stepped up by a transformer and then recti-fied to high voltage D.C.

Analysing Magnet supply 1B 2.5 Amps D.C. regulatedpower supply.

The ion implantation facility has been used for:

a) fabrication of p-n and n-p diodes and solar cells

in our section

b) fabrication of nuclear particle detectors for TechnicalPhysics Division

o) fabrication of solar cells for I.I.T. Delhi

d) Argon impl&nts have been carried out in steel forcorrosion studies for R.R.C.

e) Phosphorus implants have been done in glass to studythe formation of phosphmosilicates in the material

f) Argon implants for mossbauer studies for HarathawadaUniversity

g) Work on implanted wave guides has been under progress.Efforts have been made to reduce the losses along the guide,which are rather high

h) I D joint programme with TIPR masks for boron and phos-phorus implants to make integrated circuits are under fabri-cation These will be used fox fabrication of componentse.g. ring counters, F.S.T.'s, veractors and resistors.

-66-

3olur cells

W and P type 111 silicon wafers with resistivities

around 10 .A-cm wore Implanttsd with Boron and Phosphorua

iona at 100 keV ronpootively. Doses of the order 5 x 10

ione/cm were uned. Imp]nntation damage was annealed in a

dry nitroflnn atmosphere upto 800°0. -Por phosphorus implant

with dose of 2.6 x io'* Ions/cm2 final resistivity of

7.5 x 10 ohm cm pyavo a calculated activity of14 214 2while for a boron implant of 5 x 10 ions/cm calculated

activity of >. 15/4. A rapid drop both in Bheet and bulk

resistivity w;ia obnerved at annealing temp- beyond 600°0.

A sharp fall i.e. from 500IXa/cm to a few a a/cm , was

also oboerved.

Low temperature heat treatment was given to the

aluminium/silicon contact to study the dependence of contaot

resistance and barrier potential on heat treatment.

It was done by Y?. hr. isochronal anneal upto 300°C by

stepa of 100°C - contaot resistance was found to vary from

300 _flL. to a few ohms.

Hi&h temp, heat treatment from 300°C to 500°C was

found to change the barrier height of the solar cell and

#rive a linen : and low resiatance I-V forward characteri-

stics, -'or phoophorous implanted cell the barrier height

was found to increase from 0.33 V to 0.5V after '/2 hr.

isochronal treatment upto 300°C. Heat treatment at 45O°C

for 10 minuted showed a further enhancement of this effect.

Conversion efficiencies for solar cells were worked

out using a 100 W tungsten lamp of known spectral distri-

bution as standard source. The cell efficiency attained

for an exposed area nf 1.66 cm (n+/p) waa about 6.755

for 7.5 JX. series resistance. Photovoltiac (I-V) chara-

cteristics tend to atraighten out at series resistance of

14 -/Z. although cell efficiency was about 5.02/5. These

observations were made on bare cel3s.

-89-

4. Van de Graaff Operations Seotion (V.A. Hattangadi,S.N. Misra, U.S. Bisht, S.G. Shukla, M.E. Doctor,S.J. Mandke, P.R.S. Rao, G.V. Bhatt, R.P. Kulkarni,R.V. Patkar and N. Fernandas)

As the Van de Graaff accelerator entered its 16th year

of almost continuous operation, the machine had to be shut down

for carrying out some major overhaul and maintenance as well

as some modifications. However, after this followed a series

of machine troubles with some serious technical problems. These

problems were eventually dealt with successfully, however and

the accelerator was run during the year for 1870 hours, of which

1107 hours were utilised for research and about 230 hours were

required for routine maintenance. In all, about 3389 hours

have been lost owing to machine breakdowns.

A. MAINThiNAMCE AND MODIFICATIONS

The major maintenance and modifications carried out during

the general maintenance period may be dencribed under the follow-

ing main heads:

i) Terminal rewiringii) Vacuum system modifications

iii) Servicing and overhaul of other accelerator components

1) Terminal rewiring: The terminal has been completely rewired

with a better circuit layout and all the power supplies and other

electronic circuits have been replaced by new compact units

previously wired in the laboratory. This has facilitated

servicing in the terminal.

The meters have been replaced with indigenous ones and

the dial illumination has been improved for better visibility

from the platform.

ii) Vacuum system modifications; The main mercury diffusion

pump on the accelerator tube has been replaced because of its

frequent failure and erratic behaviour by an oil D.P. having a

larger pumping speed, 2400 £/sea. than the earlier one.

-9U-

The DC 705 silicone oil used ensures little back streaming

because of its low vapour pressure of 10" Torr.

The auxiliary diffusion pump near the analysing magnet

has been shifted to a point directly in line with the beam pipe

thus increasing effective pumping speed in this section. New

elit-viewer assemblies have been installed on two of the ports

of the switching chamber. All the A-K couplings in the beam

line have been replaced with standard brass flanges with 0-ring

gaskets. A new fore vacuum line ha3 been installed for backing

the D.P.'s and a 4" line has been put for roughing the main

accelerator tube. All these measures have improved the vacuum

system performance in general and we have not had any serious

vacuum problem since then.

iii) Servicing of other accelerator components

(a) The charging power supply and the switching magnet supply

were both rewired with some modifications in layout. The con-

stant current unit, balance amplifier, NMR Gaussmeter and fre-

quency counter were all tested and serviced.

(b) The belt-drive motor, the D.C. generator, the air compre-

ssor and the kinney vacuum pump were all overhauled and servi-

ced. The alternator in the terminal was also overhauled.

(;•'* All the column resistors were checked individually and

replaced where necessary.

(d) Both the air-drying units and all the high pressure gas •

valves in the gas handling system have been regreased and

serviced.

(e) The overhead crane for the pressure tank was also servi-

ced and given the annual maintenance schedule.

B. MACHINE BREAKDOWNS

A number of technical problems were encountered in deal-

ing with machine breakdown, some of which were quite baffling

-91-

and took considerable time to diagnose. One such problem

was concerned with the ion source yield which was quite

normal when the source was checked prior to closing the tank

but reduced to zero when the tank was closel and pressurised,

although all the voltages monitored showed that operation was

normal. At first it was suspected that the observed phenomenon

could be due to microleaks, oscillator failure or alternator

loading un^er high gas pressure. A few more meters were

added to monitor some more parameters, source plasma studied

through a portable spectroscope and mains was supplied from

an external alternator to eliminate the above causes but to

no avail. Finally, after a prolonged investigation the

fault was traced down to a faulty wirewound resistor that

would open only under high gas pressure.

The second recurring problem was failure of the osci-

llator tubes in the recently developed 100 Watt H.F. oscilla-

tor unit in the terminal. The tubes worked continuously for

hours without failure on the test bench but did not last for

more than a few days inside the tank. This was caused by

excjosive heating because of the inadequate forced-air cooling

provided by the moving belt inside the tank. The fault was

corrected by adding finned heat sinks on the oscillator tubes

and reducing plate dissipation by operating at a lower power

output.

A major problem, which accounts for most of the time lost,

occured during the alignment of the analysing magnet, which was

undertaken aa the ion beam was frequently found to enter the

magnet off the axis and had to be steered by means of small

permanent magnets at the magnet entrance. However, during the

realignment process we found that no matter what the magnet

setting is the ion beam did not emerge from the analysing

magnet strictly along the horizontal but at a slight angle

towards the ground. However, after considerable efforts,

it was realised that either the angle between the entrance

-92-

and exit pole edges or the field distribution in the gap

was not correct to give an exact 90° deflection and that,

in fact, the ion beam had to enter off-axis to make up for

the discrepancy.

C. DEVELOPMENT

A Wien Velocity Filter - a duplicate of the one in UBO in

the terminal has been fabricated and is being tested on the

test bench. It is proposed to make a detailed study of the

device acceptance and transmission as well as focussing of

the einzel lens. It is also proposed to develop a P.I.G.

ion source for use in the terminal in place of the present

R.F. ion source. An ion beam scanner and steerer are also

under design.

5. Non-destructive estimation of boron in aluminium(Y.D. Dande and N.G. Jain)

Commercially available aluminium contains ppra level bo .'on

oc'.r!;aminant3. for use in reactor compenonts, this concentra-

tion of boron has to be below 10 ppm. A technique of estima-

ting the boron concentration, preferably non-destructively,

is repaired for a quick assessment of the available aluminium

stock.

An attemptwas made, to use solid state track-e«ch

detectors for this purpose. The technique consists of sandwich-

ing a film of thin cellulose nitrate (Kodak Pathe LR-115)

between the Al sample and a perspex holder and irradiating

the sandwich in a neutron flux. The He and Li nuclei from

to vthe reaotion B(n,«;)'Li leave damage tracks in the plastic

which can be made visible by etching the plastic in KaOH.

Oare has to be taken to subtract the background tracks due

to other competing processes like proton recoil in the plastic

itself.

-93-

Inifci'il irradiation in one of the reactor beam holes

showed hi{;h background track formation. The experiment had

to be shifted, therefore, to the thermal column of Apsara

reactor. It was also realized that to eliminate errors due

to counting criteria, variation in plastic behaviour, uncer-

tainty in flux determination etc., it is necessary to make a

relative estimation against a standard of known boron content.

Five samples of Al tubes (A, B, C, D, E) obtained from

H-5 project were irradiated one by one in the Apsara tberraal

column (9.3 x 10 n/cm /a) for 30 mm each. Samples A & B were

spectroscopically analysed for their boron content and A was

chosen as the standard for all other dieasuremente. The

plastics were etched in 2.5 N KaOH at 60°C for about 30 mm,

and the track densities were measured under a magnification

of 450. The computed B concentration in the 5 samples was

70, 115, 108, 90 and 107 + 2O5& ppm respectively.

6. Converter screens for neutron radiography (Y.D. Dandeand S.ii. Chinchanikar)

Neutron radiography with track-etch detectors need Li

or B loaded screens for converting neutrons into o<-particles.

A programme to fabricate durable, high efficiency converter

screens in the laboratory wa3 undertaken. Lithium carbonate

or metallic boron powder was thoroughly mixed in a solution

of polystyrene in chloroform and the homogeneous mix was

uniformally spread over a flat metal surface with a special

jig. Experiments with natural Li and B have indicated fea-

sibility of making fairly uniform screens (+ 30 U) with this

technique.

7. Nuclear Radiation detectors

(a) BF3 and He-3 detectors (R.3. Udyawar and G.V. Shenoy)

50 BF3 detectors were made and supplied to various users

in BARC. Special achievement is the successful fabrication

of a tiny, 6 ram di-% x 12 mm sensitive length BP3 detector

for B.R.P. section.

-94-

A 50 mm dia x 275 mm long He-3 detector was developed

for use in oil well logging at Ankaleshwar. Thia detector

haB almost twice the efficiency of a bank of 8 Russian made

detectors, in current use by ONQC.

(b) Soft X-ray detectors for Mossbauer spectrometry(G.V. shenoy}

50 X-ray proportional counters were made and supplied to

various users in the country.

(c) Position sensitive detectors (Y.D. Dande and G.V. Shenoy)

The development of a linear position sensitive detector

continued. Changing to a carbon-coated quartz anode (350-IL/mm),

the linearity region was extended to 350 mm (in a 450 mm

detector) with a position resolution of fi*8 mm FVBK. Further

improvement is continuing.

8. Laser Plasma Tubes (S.R. Chinchanikar and M.L. Baneal)

A 25 mtf He-Ne laser plasma tube had been successfully

fabricated last year. A second one was made for RHC at

Madras this year.

A new He-Cd laser plasma tube was fabricated thia year.

The tube has be«n in operation at a steady power of 50 mtf at

a wavelength of 4416 A.

9. Low Energy X-ray Tube for Energy Dispersive X-rayfluorescence Analysis (3.K. Kataria)

As a part of our energy dispersive fluorescence programme

(BtfDXRF), we have undertaken the development and construction

of a low po-rer X-ray tube. The excitation of a sample by the

X-ray tube, results in comparable sensitivity in only a tenth

to one hundredth of the counting time, as compared with the

normal radio-isotope target excitation. The basic design of

the X-ray tube shown in fig. 9 follows closely that of Jaklevle

-95-

©t al '. She principal advantage of this type of tube is

the ahillty to produce X-ray fluxes to three orders of

High VoltageFeed through

Teflon

Colllmator

• V. Pumps

Intermediate VoltageElectrode 300~5004VeInsulator

Fig.9 Basic design of the X-ray tuba.

magnitude higher than those obtained with convenient radio-

isotope sources while dissipating only a few watts in the

tube. Furthermore the variety of possible anode materials

and range of currents in the tube make possible optimum

choice of exciting energy and intensity for particular

applications. The X-ray tube shown in the figure is de-

mountable and is to be operated in the transmission mode.

In this mode, the Bremsstrahlung component of the X-ray

-96-

flux relative to the characteristic K-Xrays of anode

material is minimum aa desired by ENDXRF,

The fabrication of all the components has been com-

pleted and the tube has been assembled. The X-ray tube

assembly waB thoroughly degassed and it gives a high

vacuum of the order of 10~ mm of Hg which is necessary for

its operation as a X-ray tube. The trial runs have shown

satisfactory electron emission from the filament. The

High Voltage Power Supply (0-50 KV) needed for the anode

is under fabrication at V.E.G. Calcutta.

1) J.M. Jaklevic, R.D. Giaugue, D.P. Malone and W.L.Searlea, Univ. of California, LBL-10 (1971).

'0* X-ray fluorescence analysis of materials (S.S. Kapoor)

Bnergy dispersive X-ray fluorescence analysiB (ENDXRF)

of a number of samples was performed with the high reso-

lution Si(Li) X-ray spectrometer employing Am, 5I

and J Pu as exciting radioiaotopes. These sample analyses

covered a number of interesting applications in areas

such as nuclear physics, geology, pollution, metallurgy

etc. 3ome typical examples of the analysis work carried

out in these areas are outlined below:

a) Analysis of rare earth impurities in thoria fuel(M. Lai, 3.K. Kataria and K.V. Vishwanathan)

In collaboration with Analytical Chemistry Division,

a study was undertaken to determine the minimum detection

limit of rare earth impurities in Thoria, which can be241

achieved with ENDXRF technique. Employing 100 mci Am

source, it was possible to detect rare earths in synthetic

mixtures from 20 ngm of Ce to 200 ng of Dy.

- 9 7 -

b) Analysis of alloys (M.Lai)

Quantitative analysis of a number of alloys contain-

ing i'e, Cr, Co, Wi, Ga. Mo, and Pb, and Co-Ga alloys were

carried out. Won destructive analysis of Ni-Ku crystal

and analysis of impurities of Ti, An, Pb in ^e,0. natural

single crystals were also carried out.

c ) 'Jrace element analysis of Ci^arrete Tobacco"OT. Lai, B.V.N. Kao*- and 3.K. Kataria)

Tobacoo from two brands of cigarettes waa analyzed1 25

with I source for trace element impurities. Concentra-

tion o:l the detected elements, K, Ca, Mn, i'e, Co, Cu, Zn,

Br, Kb, Jr, Zr and Pb present in the two brands were com-

pared, iiore details are given in the report B.A.R.C.-959°d) Analysis of Minerals from Geological Purvey of

India (G3lJ (3.K. Kataria, Kekha Govil, K.V. Vishwa-nathan and R.K. Chowdhury).

Trace element contents in fourteen carbonatite ore

samples from G3I were quantitatively analyzed with thin

sample technique. The trace elements detected were Ti,

V, Mn, Fe, Cu, Zn, Sr and Ba. The soectra were computer

analysed to determine element concentrations.

e) Analysis of J?VC tubings (K.V. Vishwanathan andHekha Govil).

Medical grade soft PVC tubings obtained by ISOMED

from different local manufacturers were analysed for their

metal contents. The following eleven elements were dete-

cted: Ti, Vi, Cr, J?'e, Cu, iSn, fb, Se, Cd, Sn and Sb. Their

concentrations were found to vary from 48 u. g/cm to 336«g

/cm . The aim of the analysis was to study the effect of

irradiation on the leachability of the plasticiser into

pharmoscopically recommended aquo, aquo-ethamotic and

oleagenous solvents used for biological investigations.

-98-

f) Estimation of Gallium In Bayer Liquid (K.V. Vishwa-nathan, S.K. lataria and R. (Jovil)

Bayer liquid produced during the manufacture of alu-

minium is a potent source of gallium and our country's

annual requirement is of the order of 0.3 tonne. A rapid

method of estimating 0a in Bayer liquid was standardized2*58

by the method of internal standard addition using Pu

(10 mci source). The detection limit for gallium in solu-

tion is found to be 3 i^g/ml with an accuracy of + 2$.e) Analysis of trace amounts of lead in soil samples6 / (M. Lai and K.V. Vishwanathan)

A rapid method for the analysis of lead in soil

samples (for pollution studies) has been standardized.

It is possible to determine lead from few ppm to few

hundreds of ppm in a short period of 1500 seconds using

Pu ' source. Calibration was done by spiking known con

centration of lead into soil samples of similar matrix

free'from lead. The average lead content in the soil

samples was found to be of the order of 200 ppm.

+ CSIR Pool Of "icer

11.. Low Temperature Laboratory

a) Helium Liquifier and Associated Work (N.S. Satya Murthy,V.K. Chopra, G. Dharmadurai, T, Srinivasan andA.P. Bagool)

The liquid helium production for this year has been

about 900 litres. This has been used for various experi-

ments including Neutron Diffraction, Mossbauer Spectros-

copy, Superconducting Magnet Testing etc. Also, about

40 litres have been supplied to the Tata Institute of Punda*-

mental Research.

- 9 9 -

b) i J u p e r c o n d u c t i n g Ma;?ieta ( N . J . Llatya M u r t h y ,V. it. C'hopra, d. Dharmadurai, T. Srinivasan andA.P. Bagool).

A superconducting magnet haa been wound from Nb-Ti

wire and has about 4000 turns. This magnet haa been

designed and fabricated so as to produce a maximum magnetic

field of about 5 Tesla in a bore of 22 mm. While testing,

this magnet showed training (the effect that a supercondu-

cting magnet reaches its short nample critical current

only after several quenches) and a maximum current of

about 100 amperes could be pansed through the magnet

after a few quenches. The curront leads used for ener-

gizing this magnet 1-ave shown (satisfactory performance.

These brass tube leads (see Fl«. 11) if provided with

the required threading at the lower end, can directly

be screwed onto the threaded terminals of the magnet.

WINDING ENDS

DETAILS AT "A"

Fig.11. Schematic sketch of super-conducting magnet.

•1 00-

After switching the magnet into the persistent mode, the

leads cun be uruscrewod and taken out of the cryostat.

Thia would cut off the heat leaks into the cryostat caused

by heat conduction through these current leads. A super-

conducting switch incorporating a manganin heater wire

wouiid over Wb-Ti has been designed and fabricated whicn

after testing will be uaed in conjunction v*ith the above

magnet for av/i toning it into the persistent mode.

c) Dilution Refrigerator (V.K. Chopra)

The *He- He dilution refrigerator has been tested

for leaks at room temperature. The tests at.liquid helium

temperatures are being planned.

12. A Cold-neutron source for CIRUS (S.K. Sinha, C.L.Thaper and B.A. Dasannacharya)

Studies on the design of a cold-Bource for a 12" dia-

ir beam hole at OIRUS, which will be a forerunner for

the source for ft-5 reactor, have been started. From the

point of view of neutron-gain, liquid methane source at

100K compares favourably with liquid hydrogen source at

ZDK, for neutrons of wavelength ^ 4 A. Liquid methane

1R safer but \tndergoes radiation damage and polymerisa-

tion. Calculations on the amount of damaged products,

due to V* -rays alone, show that the moderator will be

damaged approximately \<f> at the end of one month, if 550 co

of liquid is circulated through the reactor and diluted

into a 50 litre liquid methane dewar.

The cold-source consists of the in-pile and the

out-of-pile sections. The in-pile section contains the

moderator pot, cold-moderator, transfer lines, shielding

material and the bismuth filter which are contained in a

-101-

vacuum-jacket. The out-of-pile assembly consists of a

oryogenerator for liquifaction of methane gas and a

storage dewar. Liquid methane will be circulated through

the moderator pot using a centrifugal pump, which will

maintain overpressure on the liquid, so as to increase

the operating range to 127K. Preliminary design of the

in-pile portion has been completed.

ORGANISATION CHART

Organization Chart andSummary of A c t i v i t i e s 1977

VAN QE GRAAFF LrtB.Head

fl.K. fCHT*

PHYSICS G30UP

DIRECTORP.K. IYtNGAR

NuuLEAft.PHYSICS

HEADPI.K. itHTA

FISSION PHYSICS StCTIOAlHead

S.S. KriPuuR

Nuclear ReactionsNuclear Sp^ctroscopy &

StructureNuclear TheoryIon Implantation Studies

Vande-qraaff Flaintanancai Operation

Isotope Separate:Tandem Accelerator Project

Experimental Fission StudiesFission TheoryNuclear TheoryX—ray Fluorescance HnalysisProton-inducad X-ray Studies

SOLID STriTi. PHYSICSHead

N.S. S<*TYH

Neutron Scatteringfiaynetic StructuresSpir< Jensity i3istributionsPhoi. I 4 Magnan HeasurementsCloldcular & Liquid DynamicsBeam—Technique Development

Light ScatteringLiquid Crystal StudiesCoinpton scatteringMossbauer SpectroscopyLou Temperature StudiesPreparation of Alloys & CrystalsTheory

Neutron and X-ray DetectorsNeutron Radiography

(Y.O. Dande)

Electronics Designand Development

(V. Singh;

Workshop

(J.N. Soni)

Administration

(T, Ramanujam)

- 104 -

NUtLLHB PHY-jIi-b ull/ISIuN bTHFF

rt. UH

1 .

2.

3 .

N-OL-•UHArtFF LHBURHTUHY:

Nucleai: React ions

I'l.Ka.KPI.

b.

A.

. libhta

. Guptabal<Jkrii>hnan. KbrekaUeKailasl-hatter jets

ftohd. I s m a i l 1

S.b

; u i

fcl.L

PI.G

R.P

PI.A

N.LU.RH.H,

. baini

. FernandezZdr Sin&h2

. binha

. Betigeri

. Arund

. tsuaran

. Rjyauuansi

. Chakraborty

. Uia

Nuclear Reaction Theory

N. !B.K,

b.C,

iarma, Jain» Jain. Pathak3

Nuclear Spectroscopy

U.I/,U.Pl,P.J.U.b.Pl.Y.

,K. Baba, Datar, Shalerao, Ambakar, Uaze. Patuardhan

4 .

5 .

6c

7 .

I o n

N. iP.K.m. i..A . L i .

n.3.S.t i .

O.K.U.K.

\lan-

V.ft.

5.G.0.3.P.R.

G.U.R.P.S.J.PI.E.H.U.

lip lantof.ion

jdiinaBhatta^haryaBhatidu/atjh'4

Kan^ara

Gaonkar5

boodDeb

•db-Graaff iiaintenancei Oparatlons

HattanyadiPlishrabhukla

Sis>h tLiundnr Rao

BhattKulkarniPlandkeDoctorPdtkar

Isotope Separator

U.A.

F.«.K.L.

HattangadiShathanaPat el

L. Shallom

Tandem Accelerator Project

Pl.K. PlehtaPI.G. BetigeriJ.N. SoniT.P. DavidPitambar SinghL.\l. Rayarappan

1. On leave to VEX.2. Student Pan jab University, Chandigarh.3 . Pool Off icer.4 . Un deputation to Jenmark.5. Raaearch jtudent, Bombay University.

- 105 -

B. FISSIUN PHYSlLb

R. RamannaS.S. KapoorQ.M. NadkarniU.S. HamamurthyN.N. AjitanandS.K. Katariafl.K. Lhowdhury1*1. PrakaahRakha Flittal

P.N. Rama RaoS.R.S. MurthyB.R. BallalK.N. IyonyarS.L. Raote

X-ray flourusconee

5.S, KapoorK.U. ViswanathanPiadan Lai

L. SOLID STrtTk. PHYblCb

1. Neutron Scattering

P.K.B.A.K.R.C.L.P.S.S.K.P.P.A.H.

M.S.

I y e n ya rDasannacharyaRaoThapurGoyalSinhaChandraUankatosh

Satya MurthyL. Pladhav Rao

R.a.U.t.

BeyumHakhecha

S.K. ParanjpeR. Uhakrauarthy

P.R. WijaydraghauanB.S. SrinitfasanPl.R.L.N. NurthyP.K. OayanidhiA.a, Qeshpandbo.L. Lhaplot

2. Liquig Crystals

K. Usha OenizP.S. ParuathanathanA.a. Paranjpu»».I. Hohta'

3. Raman Scattering

A.P. RoyU.C. Sahnifl.L. Bansal

4. Wo'sabauar Studies

P.K. IyengarK.H.P.H. RaoS.C. BhargauaN.K. Jaggi

5. t-iectronlc States

U.C. SahniP. Chaddah

6. Lou Temperature Physics

M.S. Satya PlurthyU.K. ChopraG. OharmaduraiT. Srinit/asanA.P. aagool

7. Theoretical Group

H. bubramanianI.U.U. Rayhauacharyuiui/.C. SahniK.\i. Bhayuat

S.L. Narasimhan

1. Research Scholar, Bombay University.

- 106 -

SUPPORTING MCILITI tS

1 • Neutron detector•

Y.D. Oande

M.C. 3ainR.3. UdyawarG.U. jhenoyb.R. Chinchanikar

2. t-J.ectroni.c3 liaalun k Qfltfalopatent

U. Singhl/.Pl. ahahft.S. KotharsV.G. GaonkacJ.N. JoahiN.O. Kaiikar

3. Morkshop

.D.N. SoniK.ft. QhallU.B. Oikshita.Ro SauiantJ.S. Chawl*C.S, Pat11V.D. San Bars

4 . Administrative

T. RamanujamVijaya RavindranathA.J. KulkarniR.S. PillaiPadmini RavindranB.R. GauharK.K. KanitkarS> Prakasan

Also with the Phasic* Group Office.

- 107 -

Publ icat ions and Papers

JUUHNrtL URTlLLtS

Solid State Physics

Pl.L. Bunsal and A.P. Roy, "Rotational Corre lat ion I n Cyclohuxanaby Raman Sca t td r ing" , Chem. Phys. L e t t s . 5J3, 813 (1977 ) .

P. Chaddah, "Mamtmtum Density of Llectrona in Liquid Aluminium",Hhys. L e t t s . A 63., 51 (1977) .

P. Chaddah and V . I . Sahni , "Compton Pro f i l es of Isomeric Cam-pounds Methyl Formate and Acetic Ac id" , them. Phys. Le t ts .4 £ , 311 (1977) .

G. Qharinadurai, "k High Flow Rate, Lou Pressure Safety Value for*He Pumping L ines" , Lryoyenics 1_7_, 702 (1977) .

N.K. Jagy i , K.K.P.M. RJO and P.K. lyengar, "Monte Carlo Study ofSpin Glass bcihaviour in Concentrated Binary MagneticSystems", Sol id btatu Commun. %±, 309 (1977) .

( j . Paret te and '.. nadhav Rao, "~>mall Angle Diffuse Neutronbcat ter inu Maaaur uments on 1/^3 ^n *"ne Temperature Range<4uO-6uOK", Sol id State Commun. 23_, 179 (1977) .

R.G. P i l l a y , P.^. Tandon, H.G. Deuare, N.K. Jagyi and K.R.P.CI. Rao,"Hyperfine I n t e r a c t i o n Studies i n Ferromagnetic RhjMnSn",Sol id State Commun. 23., 439 ( 1 9 7 7 ) .

V.C> Rakhbcha, R. Chakrauarthy and N.a. aatya Murthy, "ApparentLou A-:>ite Moment in re^O^", 3. de. Phys. 3_e, C1-107 (1977 ) .

A.P. Roy, "Laser Raman Spectrometer", Phys. Neus. 8 , 14 (1977 ) .

A.H. tfenkdteah and K.H. Rao, "A Simple White Beam Neutron D i f f r a -c t ion Technique", Pramana £ , 1B4 ( 1 9 7 7 ) .

Fiasion Physics

M.N. H j i tanand, "A Semi-empir ical Expression for Specif ic Lumine-scence in P las t ic a c i n t i l i a t o r s " , Nuclear Instruments andMethods | £ 3 , 345 (1977 ) .

S.S. Kapoor and R.K. Choudhury, " I n t e r p r e t a t i o n of Fiasion Frag-ment Anisotropies in the Fission of 2 3 8 U Induced by I n t e r -mediate tnergy * He Ions", Phys. Rev. Cj j j , 459 ( 1 9 7 7 ) .

S .S . Kapoor, U.S. Ramamurthy, M. Lai and S.K. K a t a r i a , "Searchfor Superheauy Lleoients Monazite from Beach Sands of SouthI n d i a " , Pramana g_, 515 (1977 ) .

- inn -

B. Kr ishnara ju lu , d.K. Muhla, H.K. Lhuudhury, U.FI. Nadkarnland ' J . ^ . Kapuor , "Yiwldu -i nd Lnar.jy Spectra of LlyhtLharyiad ^JrticJoB imjttfcd in Ndutron Jnduc ad f i «s ion of<JS>u", Pr«niana U, J1L. (19/7 J.

U.b. Ramamurt.hy and j . b . Kapuur, "[ .valuation of Nuclear ShallLorrtut-iun Loui yie s fur R e a l i s t i c -ichems a by TemperatureSmn<u iny Pluth.id", Ptamana 9 , 6 U (1977 ) .

U .J . Hsmamurtliy, H.K. Lhucidhuiy and J . t . liuhankr i shna, "Studiesuf Proiipt tinmniii Kjy Flul t i p l i c l t y L)i9tr lbotlans In bponta-nboin Fissiun of *$2'Cr", Pramana B , J22 (1977 ) .

Nuclear t'hyolia

5.K. Gupta, "Hiyh rtssolution Gamma-Hay bpecttum from Concreto",Nucl . i c i . 4 tnyy . fa3_, 19J ( 1 9 7 7 ) .

B.K. Jain and b,L. 5hah, "btruny Absorption Model for Pion InducedKnoukuut HB.ictian", fvucl.;ar Phyoics ft 3u2, 4 0 1 , (1977 ) .

N.L. Ju in , "Ac t iu i t i as in Nuutron Radiuyraphy at Trombay", A not*published in Neutron Rarti oyraphy Newalettei ±5_, 1 (1977 ) .

S. Kallas and S.K. Gupta, "Volume In tegra ls of Nuclear AbsorbingOptical P o t e n t i a l s " , Phys. L e t t s . 71B, 271 (1977 ) .

("l.K. f luh ta , b. Kd i l as and K.K. bhekaran, "Total ( p , n ) ReactionLraas—boLtiun Study on •>'tf outjr the Incident Energy Range1.56 to 5.53 M B V , Pramana J3, 4 19 ( 1977 ) .

n.A. flahroan, !"!.*. Aual , H.l<l. Ben Gupta and S.K. Gupta, "TheSpin-Par i ty Aasiynmunt to the Resonance Lewsl 13.980 MBUi n i a b i " , Nuuioar Sc i . 4 App l ica t ion Supplement-1 ser ies B,p.77 (1977) .

CI.M. Rahman, 11.* . Aual , I*). Rahman, H.i1). ban Gupta and S.K. Gupta,"Hiyh Hoso^ution Gamma-Hay bpec troscupy of the 2 7 A l ( p , r ) 2 8 S iRusonanca React ion", Pramana ti_, A/ti ( 1977 ) .

fri^LRb PHLbtNTLJ XT LUNFt.HtNi.L5 riNu lifcLTXNUa

iiol id State Phyaics

Nuclear Physics end Solid State Physics byropualum (DttE)f Poona,Uece'iiibu'F "1977

Cl.L. Uanaal, "i\ He-Cd Laaer for Raman Studies".

M.L. Banual and ^ . P . Roy, "Rotat ional Correlat ion in Cyclohsxaneby Raman bca t te r ing" .

1*1.L. Bansal, \j,L. oahni and ft.P. Hoy, "Space Group Changs Accom-panying Order-Disorder Transi t ion in Cu(NH L e i .2H-0" .

- 109 -

P. Chaddah, "Llectrun Momentum Oensity studies and Comptonbcatturiny".( Inulted Talk)

R. Cnaki Juarthy, L. Nadhau Rao, 1. Jirak and N.S. Satya Plurthy,"fiomunt Distributions in Nickal-Ruthenium Alloys".

b.L. Uhaplot, K.R. Hao, A.H. l/enkatesh and P.R. Vijayaraghauan,"Lattice Dynamics of cst-Potasa ium Ni t rate" .

i/. Chopra, "Ultra Lou Temperature Techniques" ( Invi ted talk inSeminar on Physics at Lou Temperature).

B.A. Qasannacharya, P.S. Goya I, b.K. binha and C.I. Thaper,"Rotational Dynamics of Ammonium Ions in OctahedralSurroundings".

B.A. 0ajannacharya and P.a. Goyal, "Rotational Torm-Factorof NH^I".

G. Oharmadurai and B.A. Ratnam, "Luolution of an Induced Hotapoton a Lony oup er—conducting Thin Film Plicrobridge".

N.K. Oayyi, K.R.P.fl. Rao and W.P. oubramanian, "A Hossbauerbpectroscopy Study of Natural Alterations of I lmenitss".

N.K. Oaggi and K.R.P.fl. Rao, "Thurmodynamics of a SimpleSite-Muenched Claynetiu Mixture".

5.K. Paranjpa, taathik N.A. Hanak and R.J. Beoum, "f lnt i ferro-muynetism in Clixed Heusier Alloy (Cu, Pd ) 2 ClnAl".

R. Subramanian and K.U. Bhayuat, "On Certain Functional Analy-t i c a l Aspects of Band-Cdye States".

K. Usha Genii, A . I . fiehta, U.H.K. Rao, P.S. Parvathanathan andA.S. Paranjpe, "Temperature Oapsndence of the DensityUolume Expansion coeff icient and T i l t Angle of H 6PA for250K <^T ^ 34UK".

K. Usha Oeniz, A.S, Paranjpe, P.S. Paruathanathan, L.B. Plirza,H«I . ftehta and K.a. Patel , "Phase and Phase Transition inthe Compounds p-n-Alkoxybenzylidene-p-Aminobsnzoic Acids".

C.L. Thaper, ^.K. Slnha and B.A. Uasannacharya, "NeutronInelastic Scattering from Glycine and DL-oC-Alanine".

O.K. Sood, fU ..Sundararaman and R. Krishna, "Blistering byHelium Ion Bombardment".

O.K. Sood, "Empirical Rules for jubst i tu t ional i ty inSurface Alloys Produced by Ion Implantation".

- 110 -

I n t e r n a t i o n a l j u i i d s ta te Ph.y3i.ua Symposium, Ca lcut ta , Jan 1977

B.A. uasannachaiya, P. b. Goyai and C.L. Thaper, "Reor ientat ionalnotion of rtinmunium Ions in bsvaral Ammonium j a l t s " .

K.H. H«io, P.K. lyanydr, H.H. Wenkateah, P.R. Vijayarayhavan and3 .F . Trevino, "Phonons in KNO ".

N.K. J a g y i , K.R.P.rt. Hdo and P.K. Iysnydr, "Nossbauer iipcctro-scojjy btudy of Ternary Hlloya Co FeGa and Fe CoGa".

K.R. Rao, i>.L. thapiot, P.K. lytnjrfr, A.H. UanKdtsbh vind P.H. l / i j jydrayhawan, "Lattice Oynamica of Potassium Nitrate I I " , Int .tonf. on Lattice Jynamici, Pjris (1977).

4th Jnternaii onaX Conference) on Hyptsrfina Interactions, Orniu Uni-versity, Cladii.on, U.~J,X.', Juhe'1.977 {"ala'o" publTshnd in Hyperfine

~TT~Z 7

N.K. Oagyi, K.R.P.n. fiao, rt.K. Grcv/er, L.C. Gupta, R. U i jaya-racjhawan and Le diny Khoi, "Mo'ssbauer and N.P1.R. jtudy ofSi te Preftironce and Local tnuironment L f fecta in Co„F8Gd andFe CoGa". *

R.G. P i i i a y , P.N. Tandon, H.G. Jeuare, N.K. Jaggi and K.H.P.M.Rao, "Hypt-rfine Mdjnetic Fialda at Rh and Sn Sites in Ferro-magnetic Rh Mnsn and Thair Temperature Uar ia t ion" .

Fission Physica

Nuciear Physics and S,uiid btatu Phy aio» aympoaium (D*tE), Poona,Oacember 1977 " •

N.N. H.jitdnand, K.N. lyenyar and S.R.S. f lurthy, "TFSO Responseto Fragments from Liyht Charged P a r t i c l e Accompanied Fissionof 2 3 6 u " .

ri.K, Choudhury, O.n, hadkaini, P.N. Rama Rao and S.S. Kapoor,"ftultipdrameter Studies of Mass, Energy and Angle Correla-tions in Ternary Fission of 235U induced by Thermal Neutrons".

H.K. Choudhury, U.S. Ramamurthy and J.C. Plohankrishna, "Multi-p l ic i ty Distribution of Prompt Gamma Rays in SpontaneousTernary Fission of 2 5 2Cf".

O.M. Nadkarni, R.K. Choudhury, j . S . Kapoor, B. Krishnarajuluand G.K. Clehta, "tmiasion of Indiuiduai Light Charged Part i -cles U = 1,2) in 120-500 KaV Neutron Induced FisBion of235 u...

- 111-

P). Prakash, U.S. Ramamurthy, S.K. Kataria and S.S. Kapoor,"Lffdct of Frictiun on Fraymont Motion Near Scission Pointand Fission Fragment Kinatic Energies".

PI. Prakash, "Transmission Throujh Biharmonic Oscillator Poten-tials: Application to Joublu-Humped Fiaaion Barriers".

PI. Prakash, "yuantitatiue Resolution of 23<i Th-Anomaly".

U.S. Ramamurthy and S.K. Kataria, "Microscopic fiodel of LouHeauy Ion Coilisiurt".

S.S. Kapour, "tharya Particle Induced Fission and Fission LikeRbactions", International Lonfurante on NuclBar Phy3ics atCyclotran Lneryies, Lalcutta (1977).

International Uonfefence on Nuclear Structure, Tokyo (1977)

S.K. Kataria, U.S. Ramamurthy and S.S. Kapoor, "Semi EmpiricalNuclear Leuel Density Formula".

U.S. Ramamurthy and S.K. Kataria, "Classical Microscopic (Des-cription of Particle Cluster Collision".

U.S. Rdniamurthy and S.S. Kapoor, "Analysis of Fission Excita-tion Functions and to Uetermination of Shell Effects atthe Saddle Point".

Nuclear Physics

Nuclear Physics and Solid State Phyaica Symposium (DflL), Poona,December 1977

V.K. Agarwal, C.U.K. Bab ha, S.PI. Bharathi, U.M. Oatar, H.C.Jain and B. Lai, "Leuel Scheme of 81Kr".

A. Chatterjee, S. Saini, S. Kail as, N. Anuntaraman, PI. Bala-krishnan and Pl.K. (Ishta, "Resonance bpectroscopy of theNucleus 4 4Ti".

O.H. Chakrabarty, N.L. Ragoovanui, H.H. Oza and PI.A. Lsuaran,"A Method of Alternate Recording of On and Off ResonanceYields at a Fast Hate to Smooth out the Background".

T.P. Dawid, Pl.G. Betigori, P. Singh, J.N. Soni and M.K. Mehta,"Voltage Testa of Tandem Accelerator at BARC".

S.K. Gupta and S. Kailas, "Microscopic Calculation ofNucleus-Nucleus Complex Optical Potentials".

A.K. Jain and N. Sarma, "Application of Thomad-Fermi Gas Modelto Strongly Damped Collisions of Heauy Ions".

- 112 -

O.K. Jain, "Scrutiny of thu Impulse Approximation for (p, 2p)Heactiun".

Pl.t. Jhinyan, K.P. Anand, S.K. Gupta and O.K. Hahta, " °"(n, 2n)and CT(n, 3n) Lroas Sections on the Baftis of Stat is t ica lModel For Haavy Nuclei".

Kiran Kumar and A.II. Jain, "Microscopic Calculation of O-Sca-tteriny Including Lxchanye Lffects".

•4- •+S.C. Phatdk and B.K. Jain, "Off Shell t f fecta in ( IT , IT P )

Reaction on 1 2 C".

S.C. Phatak and B.L. Sinha, "The Imayinary Part of Nucleus-Nucleus Potential".

S. ia in i and M.R. Gunya, "Hiyh Spin Stutus in 4 5Sc".

Gulzar Singh, S. Kuilas, A. ChatterJea, b. Saini, ri. Balakriahnanand Pl.K. Mehtd, "Fluctuation Analysis of 4eCa (p, n)48Sc Totaltxci tat ion function from 1.9 to 5.1 del/".

P. Sinyh, A.K. Jain, T.P. David and fi. G. Batigeri , "Ion Opticsfor Accelerating Tube of 2I"1U tandam Accelerator".

Bikash ainha, "Iujcleu»-Nucleus InLwraction Potential" ( Invitedtalk in Seminar on Optical Potential ) .

Bikaah Sinha, "Nuclear Friction and the Imayinary Part of thsNucleus-Nucleus Interaction Potential" .

R.I/. Srikantiah, H.J. bhetty, P.K. Bhattacharya, S.G. Gaonkarand Horace ft. Aniayyei, "Studies of Ion Implanted Semicon-ductor Detectors".

Proc. International Conference on Nuclear Physics, Tokyo (1977)

PI.A. ttwal, PI.A. Rahman, H.M. bun Gupta, G.O. Oin and S.K. Gupta,"A 7/2 Heaonanca in 55Co".

L.U.K. Baba, U.N. Oatar, l/.K. Bharyava, R.H. Iyer, S.G. Clarathaand <J.K. Rao, "Search for Bound Pol yneutron Nuclei in thefission of 2 3 6 " .

rt.K. Jain, "A Stat is t ica l Interpretation of Large Energy Trans-fers in Heavy Ion Collisions".

A.K. Jain and N. Sarma, "Finite Range OUBA Calculation for thaD(d,t)H Reaction".

S. Kailas, N.K. Ganguly, O.K. fiehta, S. Saini, N. Vesrabahuand Y.P. Viyogi, "bpectroscopic Factor from the Study ofIsobaric Analog Resonances Through (p,n) Reactions".

- 113 -

I*I.K. Plehta, A.L. Athouyies, A. Chatterjaa and S. Ka i l as ," I x c i t a t i o n af ^hapii Idomera in Uranium Isotopes".

S. Sdini and b.K. Uupla, "Global t f f u c t i v e In teract ion fromSimple Mucluar Spuctra".

N, barma, "Luwdls in • Aa Throuyh a Proton Transfer Raact ion".

N. barraa, "A b t a t i u t i c a l In tyr pre ta t ion Df Large Energy Trans-fers in Heauy Ian C o l l i s i o n s " .

B u l l . Am. Phya. Sou. 22 (1977)

PI.A. tsuidran, H.t. Uore, H. Look and J.P. Draayer, "A Study ofthe RtMution 1 ;lF(6Li,d )i3Na dt 36 rieU".

FI.A, tbuarsn, H . t . lioro, "Sys tamatics of Ground btata Alpha-Liuator bpuctroscopic btrenyths for Odd A s-d Shel l N u c l e i " .

CI.M. Lswj.dn. C. buyontidk t r , H .N . Boyd, R. Cook and H.C. Gore,"The 1 t 5 O ( 6 L i , d r ) Ruaction".

H . t . Gortj, n.A. tuuarcin, R. Look and N. Rust, "The Reactions2 V « l ( 6 L i , d ) 3 1 P and J 1 p ( 6 U , d ) 3 5 C 1 " .

In tBrnat lonal boldr Lnoryy Conyraas, Delhi (1977)

N. Sarma, "Ion Implanted boldr C e l l s " .

N. Sarma, " U l t r a - u i o l e t Absorption Produced by Phosphorous IonImplantat ion of Fused b i l i e a " .

N. Sarma, "Applicatiofi of the Thomas Fermi Gas Model to StronglyDamped Col l is ions of Heavy Ions" .

A.K. Ja in , " S t a t i s t i c a l Approach to Heavy lun C o l l i s i o n s " , Inv i tedTalk , I n t e r n a t i o n a l Symposium on Nuclear Physics at Cyclotront n e r y i e s , Ca lcut ta , September 16, 1977.

N.C. Ja in , "Neutron Radiography with Track-Etch OetBctors", Paperpresented at the Symposium on "Isotope Applicat ions i nIndustry" , Tromtiay Feb. 2-5 (1977) .

- 114 -

RtPORTS Iiii»Ui.D

A. Chatterjes, rt.L. Mthougies and O.K. Plehta, "Stat ist ical l«lod»lCalculation of fission Isomer Excitation Functions in (n , n ' )and (n, Y ) Reactions", B.rt.R.C. Report No.936.(1977).

S.K. Kataria, S.S. Kapoor, N. Lai and B.U.N. Rao,,"QuantitativeAnalysis with Lneryy Diapersion X-ray Flourescenca Analysis",B.A.R.C. Report No.959 (1977).

THLSib

The following theses were submitted during the ysar for the awardof Ph.O degree from University of Bombay:

P. Chaddah, "Compton Scattering oC Some Studies on ClactronMomentum Densities in Solids and Liquids" - Ph.O degreaUniversity of Bombay.

V .U Rakecha, "Spin Density and Spin-Uave Dispersion tnvastlga-tions in Some Claynetic by a turns Using Neutron ScatteringTechniques" - Ph.O thesis University of Bombay.

- 115 -

Seminars

ih LULLUMUIA nj

"Non Linear Uptiua: Two Photon Absorption and CombinationFrequency liunerat iun", H.V. Fan, Purdue University, U. 5. A,Jan 6, 1977.

"Smniclaasical Theory of Heauy-Ion Transfer Reactions",H. Hasan, Tata Institute of Fundamental Research,Jan 18, 1977.

"Exporimantal Te»t of Kinetic Theory of Dense Fluids-TeatParticle liution and Density Fluctuations", Sou/ Hsin Chanand Sidney Yip, Oept. of Nuclear tnyineering, MassachusettsInstitute uf Tectmuluyy, U.b.A, Jan 19, 1977.

"Particle and Nucluar Physius from .Huon Capture", N.C. Mukhopa-dhyay, SIN, Zurich, Jan 28.1977.

"Recant Proyrusa in Positron Fermi burface and momentum Densitywork", P.t, Mijnarends, Reautrum Centrum, The Netherlands,Jan 28, 1977.

"Intaraction of Pi-mesons uith Nuclei", S.C. Pathak, Universityof flanchester, Feb 1, 1977.

"Some *spect8 of Neutron Scatteriny from Magnetic Systems",T.J. Hicks, University of Oonash, Australia, Fab 3, 1977.

"Three-Deimen^ional Structure and Function of Carbonic Anhydraaea",K.K. Kannan. Uallenbery Laboratory, University of Uppsala,Sweden, Fsb 21, 1977.

"Amorphous Solids", B.R. tolus, imperial College, London, Feb 25,1977.

"Highlights of Present-Day Nuclear Physics txperiments withAccelerators", N.K. Ganguly, UEC Project, BARC, March 1, 197".

"Photoelectron Spectros<<:opy (UPS, ESCrt) of Solids"', C. Ghosh,Opto-Cluctronics Section, E'rtflC, March 29, 1977.

"Liquid Crystals and their Applications", K. Usha Deniz, NuclearPhysics Division, BARU, npril 5, 1977.

"The Theory of Anolastic Relaxation", M. Balakriahnan, ReactorResearch Centre, Kalpakkam, April 6, 1977.

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"Accelerators at Lawrence Berkaly Laboratory", 0.3. Clark,L6L, Berkeley, April 12, 1977.

"Excitation of Shape Isomors in Uranium Isotopes",Mrthur rtthoyius, Nucluar Physics Division, 6ARC,April 14, 1977.

"flossbauer Effect Investigation on. Hemoglobin and itssubunits", Ambuj Plukharjes, City of New York, U.S.A,April 26, 1977.

"Phaae Transitions Involving Configuration nixing",

Flustansir Oarma, Theoretical Physics Group, T.I.F.R,Aoril 26, 1977.

"Ion Implantation in Semiconductors", Amitabh Jain, Centre forApplied Research in tlactronics, I.I.T., Delhi,April 27, 1977.

"Spin Glasses", Deepak Kumar, Hoorkee University, Roorkes,June 20, 1977.

"Photon and Electron Induced Fission of Even-EvBn Actinid8«",8.b. Bhandari, Pahlavi University, Shiraz, Iran,*ug 16, 1977.

"Report on the Accelerator Conference huld at Serbukhov, USSR",A.S. Divatia, VEC, Calcutta, Auy 19, 1977.

"Application of Inelastic electron Tunneling Spectroscopy (IETS)to Radiation Induced Degradation of Organic l*lol acules",Oihir Parikh, 1BPI, T.3. Uatson Research Centre, New York,U.S.A, Sept 17, 1977.

"Highlights of the International Conference on Nuclaar Structure,Tokyo", C.l/.K. ttaba, Nuclear Physics Oiuiaion, BARC,Sept. 27, 1977.

"Towards Absolute iero", O.U. Lounasmaa, Helsinki University,Finland, Oct. 28, 1977.

"Exchange Correction to Electronic Dieluctric Function of, RealCrystals", H.P. Singh, I.I.T., Pouiai, Bombay, Due. 13, 1977.

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IXLTURllb rtNQ Stl'lIMBS

Lectures and iumindra dulii/ered by members of the Ciui9ian,other than thuiu inuludwJ in Physica Colloquia at BARc arej

Solid btate Physica SuutiunaX Samlnars at BWRLi

"Auouatic Holoyri i ' jh/", U.i.. t>ahri, j : n i 5 , Feb 3 and Clarch 5, 1977.

"Ccyabal Fluids in Alloys by Neutron Scatter ing", R.J. Beyum,Fbb 18, 1977.

"Trends and Proapacts of Appliedtion^i of Thermal Neutrons",K.R. Hao, Fdb 25, 1977.

"Raman SuJtteriny from Clalecular Liquids", M.L. Banssljflarch 19, 1977.

"Polarisud Neutron ijtudy uf Ni -Ru , Hlloy", I. J i rak,Apr i l 1, 1977. 0 < 9 7 U ' L ' 3

"Greun's Functions", K.V. Shayu/dt, rtprii 19, 22, 26, 29 andClay 4 , 1y77.

"Some New Spin Glass bystum3", N.K. J-iyyi, July 8, 1977.

"ftaynutit: Propert i ja uf Mutinidea", H. thakrauarthy, July 19, 1977.

"Tunndliny SpeiL-troscopy", U.K. Lhopra, Auij 26, 1977.

"Applicat ion uf Gaen'ii Function Wuthod ta i lec t run States inSolido", P. Lhadddh, rtuy 72 and 19, 1B'77.

Seminar on Nuutrun bcattering UjnUuutad by ,'ndjan Phyaica Aaaocla-t ion (fiomtjay Lhaiptar), Doc 3. 1977

"Introduction to Ntiutron Scattar iny", K.R. Rao.

"Study uf B io loy ica l l ioleculus", A.S. Sequuira (membar of NeutronPhysica Div is ion) .

"txpsrimentdl Techniques", L. Fladhau Rao.

"Study of Non-mdgnetic aol ida", C.L. Thaper.

"Playnetic rtspucta", 'J.C. Hukhechd.

"Liquids & I'loleculBa - some examples", B.rt. Uaaannachatya.

"Nuui Techniquus", fi.H. Satya Plurthy.

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Seminar on Mork at Liquid HoUiwi Temperature hold at BARC onOct 11. 1977

"Introduction to Philips Halium Liquif ier", N.S. jatya flurthy.

"Suparconductivity and Magnetism", U.K. Chopra.

"Tunneliny Spactroscopy at Lou Temperaturaa", B.A. O«sannach«rya.

"Ultrasonic Attenuation Studios at Low Temperatures", P. Chaddah.

"Superconducting Thin Film Flicro-Bridges", C. Uharmadurai.

"Oilution Refrigerator and mtra-Low-Temperatura Technology",

U.K. Lhupva.

Heavy-Ion Uorkahop hald between Feb 1977 - Mug 1977 at BARC

"Deep Inelastic Collision between two Heavy Ions"

I - Currant Status of £.xpsrimant» in Heavy Ion Coll ision*,S.b, Kapoor.

I I - Macroscopic Descriptions of Hea>:y Ion CollisionDynamics, U.S. Ramamurthy.

I l l - Pluchaniam of Class txchanye in Deep InelasticCollisions, S.K. Kataria.

"ntcroscopic Theoriaa of Heavy-Ion Collision Dynamic*"

I - Linear Response Theory, B. Banerjee, from T. I .F.R.

I I - Phunomanalogy and Response Theor-', B. Sinha.

"Imaginary Part of che Ion-Ion Interaction Potential", S.C. Phatak.

"A Simple KineroJtical Clodel for Energy and Class Transfsr inHeavy-Ion Collision", A.K. Jain

"Neutron Radiography", N.C. Ja in , a t Training Course i n AdvancaCourse in Indus t r ia l Radiography at BARC.

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Uthar Scienti f ic Act iv i t ies

Thu members of thti Uivisiun have been actively involved in

Teauhiny and Training Proyramrnes, uryanisatiun of Symposia and

have served on various committees of the Department of Atomic

inorgy, Universities and thu Indian Physics Association. A brief

account of those <Jcti i/itios its as follows:

TtMLHIMG HNJ TRAINING

Like the previuus years, uarioua cuursos in Nuclear Phy8ic3,

i o l i d Jtatu Physics and Uuantum Piuchani a wore delivered to the

traineua of the 6.M.R.C. Training School and poat graduate students

of tha Univurciity of Bcimbay.

Traininij fur Mutionai Scitmce Talant Soarch Scholars and

fbfroaher course for Pofat Graduate Univoraity Teachers mere al3o

artdnyuj. These |jroyrdmmaa art a ruyular featurs duriny the summer

and are constantly revisfad in ducordance with the feedback from the

recipients.

fur several years, (numbers of the Oivision havu been organising

the Nuclear Physics and the Solid State Physics Symposium of the

Department of Atomic Lnuryy. This is a National Symposium, held

every year towards the end of Oecumber, in which the members of the

Physics Community from all over the country get together and discuss

their work. This year's Symposium uds held at Poona University,

Pune during December 27-31. The Convener and Secretaries of the

iymposium are from this Division. The proceedings of the Symposium

are published undur their guidance.

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AND HLaLrtKCH but)l£a

Plemtiurs of the Division hdi/e bean actively involved in the

promotion of sc ient i f ic and research ac t iv i t ies in the Country and

havt* bean serving on several national committees. During the year

of this report they have been connected with!

Research grants and Scholarships to Universities from the

Board of Kesearch in Nuclear Science of the Department of Atomic

tnaryy;

Ut i l izat ion of the Variable Inergy Cyclotron at Calcutta}

University Grants Commission's ad hoc Committees for special

assistance programmes to Universit ies;

Board of Studies for Physics and Selection Committees for the

teaching Staff in several Universit ies;

Indian Physics Association, both in i t s National Committee

and Bombay Chapter.

B. A. R C.-I012 GOVERNMENT OF INDIA TtHTHJ 3v3ff 3T(4H ...

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