Spin assignment, to the 2.23, 1.98,1.88,1.41 and 1.07 MeV levels of Sb125
has been made from directional angular correlation measurements

Bhattacharyya, R

Nigam, A K

English

IACS Institutional Repository

GAMMA-GAMMA ANGULAR CORRELATION IN Sn'“A. K. NTGAM and R. BHATTACHARYYASAifA I n s t it i t t e  o f  N u c i e^ a h  P h y s ic s , ( 'a l c u t t a , [ n p t a .{Received Janm fri/ ir>, 1905)ABSTRACT. Spin assignment, to tlu* 2.23, l.ftS. 1.88; 1.41 and 1.07 MeV levels of Sbi-iB has been made from directional angular comdAtioii measimunents.I N T R O D U C T I O NThe levels of excited tlirougli the decay of liave benm previously studied by several authors (Nuchuir Data Sheets, 19b4, Dovarc et aL, 1964). The spin-parities of those levels were as(u‘Ttained mainly from the knowledge ol tlie beta- de<iay log ft-values. In the present work the spins of some of the levels have been determined from y —y  angular correlation experiments.The experimental sources were' prepared in small thin-walled j)crsp<‘X con­tainers from chemically processed Sn^*^*'* obtained from the Oak Ridge National Laboratory. The 9.4 min activity of Sn^ *^  ^was allowed to dt c^ay sufficiently before^  the chemical separation was carried out in order to get rid of some Sb ‘^^* activity formed ther(*froin. The activity of Sb^ ^^  accumulating from tlu‘ de(;ay of the 9.7f/ was not large (moiigh to disturb our im^asunmients within the shorttime in which the experiments were performed.E X P E R I M E N T S  A N D  R E S U L T Sy - y  angular correlation between five cas(^ades, shown in Table I has hmn measured. The spins of the 2.2:i 1.9S, 1.S8, 1.41 and 1.07 MeV levels were deter- mined. As it w^ as not possible to study th(^  short lived isomer of &n^ ‘^®, the spins of the levels at 0.325, 0.640,0.910,1.470, 1.720,1.940 MeV could not be detennined. The summation technique of Hoogenboom (1958) was used to separate the peaks more effectively from the general Compton background and from other adjoining peaks. Fig. I shoves some of the representative spectra measured with the help of this method. The spectrum of Fig, 1(a) was recorded with the sum channel set at 1.8-2.1 MeV region. As both of 0.81 and 0.91 MeV y-rays are in coincidence with the 1.07 MeV y-ray, they, with their respective intensities, contribute to the area under the 1.07 MeV peak. The prominent peak in Fig. 1(b) is due to the coincidence between the sum-pulses at 1.41 MeV (=  1.07+0.34) and 0.34MeV y-ray. The second peak in the same spectrum arises due to the, straightforward coincidence between the 0.47 MeV y-ray and the y-ray of 1,41 MeV energy selected25215216 A. K . Nigam and K. BhaUacharyyaiilotig 'witli th(“ .sujti-[hi1ki‘(j. Tii ov(U*r to iiicivaiic the* untlt r^ the 1.16 MpVpeak shown in P'lg. 1(<1). a hm ad seh'etion was made, in tlic sum channel(2__2-3MeV) which adm itted  some of tlu sum -pulses of the  0.81 — 1.07 and(),91_] .07 MeV cascwles resulting in an inereaM'in the area under the 1.07 MeV peak.(b)§Kip. 1. Solid CurvoR : Ho<>p<‘nboom-Hpoctm of tbo y  myH n< Oettod Curves: Spof’tmroeorded in 1 he straiplitforw urd irmiuior. m the region of iniereHt tiavebeen Shown.The oorrolation (>txperiin(‘n t porloniK'd with spoetra in th e  (‘hannolsiiet'd little  correction due to  o ther p('rturl)ing radiations. However, for th e  weak intensity  (cascades, statistical acciira(*y in tlu^ r(‘Sidl (oiild not he increased suffi­ciently. M easiircnients \\(*r<' also condm tiMl using tin* conventional slow-fast coincidence m ethod for all the  casca(U*s c>xc(‘p t the* I.Hi - 1.07 MeV  ^ one and essen­tially  sam e ri',Milts weri^ obtained. Tlu' A.^  and  (uieflicicntt wore (calculated a(c(cording to  tlie form ulation of Rose ( L95H). (hcometry correction was m ade from the  curves by Stanford and R ivers (1959).TARLE JElx])(*riinental results( t^iHoadoMoVSum chamud sottingA>Kxp.A .Exj).PossibleAssignment0 .8 1 - 1 .0 7 I 8 0 -2 .0 0 0 131 i O . 032 - 0 .0 4 6 ± 0 .0 5 13/2(3)7/2(1)7/20.91™ 1.07 1 9 0 -2 .1 0 0 1 7 6 ^ 0 .0 3 ! - 0 . 1 l l ± 0 . 0 5 11/2(2)7/2(1)7/20 .3 4 -1 .0 7 1 .35- 1.45 0.031 ± 0 ,0 3 6 0 .0 3 7 ± 0 .0 5 11/2(2)7/2(1)7/20 .4 7 -1 .4 1 1 .8 0 -2 .0 0 - 0 .0 7 S ±  .078 - 0 .0 2 6 ± 0 .1 2 13/2(1)11/2(2)7/2fll/2(2)7/2(l)7/21 .1 6 -1 .0 7 2 0 0 -2 .3 0 0 .0 8 4 ±  0.083 0 .0 1 9 ± 0 .l( )  ■(ll/2(2)»/2(l)7/21 9/j(2)9/2(l)7/jD I S C U S S I O NThe ground s ta te  of and  have been assigned on th e  basis of single particle shell model (Goldliabor and  H ill, 1952). The b e ta  spectrum  of 9.7d gj^i26 m easured w ith  a  Sieghbahn-Slatis spectrom eter. The end-energiesQamma-Oamma Angular Correlation ' in Sn^ ^^ 217and log ft-values were found to  be in accord ^vith these previous results (Devare (4 aL, 1964). The spin assigimionts to tbe levels of the present measure­m ents shown under J\ry{^) \ in Fig 2. are compatible with both log ft and angular correlation data.J [ y .7 '( 0 ) ]  11/2n/213/211/27/27/2r5otoCD_  ^ in\ 1“ V..Ch656 1-----35611119 5 7|wiI1:__ ±_j51 Sb 2 YrsB(MeV) 2 23 1 * 9 8  1-94  1-88 1 * 7 21 * 4 71 - 411070-910 * 6 40-329/2,11/2 9/2,11/2 3/2,5/2 9/2,11/2 3/2,5/2 3/2,5/2 7/27/ 21/25/2,7/25/27/2Fif?. 2. Proposod lovel-snhcme olE xplanation  of tlie lovol spootrum oi' was suggostwl by Silvorborg(J061) on the  basis of tl.o coupling bclMciai the g, ,  and </„,■ , odd jirotons with the, hanuonio v ibrath .n  of th e  2 - one jilionon excitation of tlie ev.m-evcn core. However th e  centre of grav ity  rule docs no t si'cm to hohl good there. In  order to make the C G. Rule fit in to  th is  scheme we reiiuire two sets of r:tates arising due to those couplings. For th e  2^ coupUng the 0. G. lies a t  J ..5 M e y  im isidying the 0.640, 1.075, 1.41 and  1.47 MeV levels of Fig. 2, in whi.di a 9/2 ' level has 1mm left ou t In  Table 1 the  1.10-1.07.5 MeV <.as(-ade shows the possibility of a .) 2 mtor- m ediate level a t  or near 1.075 MeV, not resolved from the 7/2 • 1.075 MeV hnein the spectrum . This would, however, suggest a mode of deeay lor t i e  • o w o  a^d  a  9/2^ level very nearly a t 1.075 Me.V. W hen th is level is taken into consi­deration the above values of C. G. comes out to be a t  1.11 MeV, fairly in agreement with th e  energy of the  2^ sta te  of a t 1.13 MeV. Some of thez T m ^ :  ^ — ... ^  . h.  . . . . .mode of couplings.218 A. K. Nigam and R. BhattacharyydA C K N 0  W L E D G M[E N TTho authors are grateful to Prof. A. K. Saha for his encouragement during the progress of the work. They are also thankful to Mr. S. Shastry and Mr. B. B. Roy for t heir helj).It E E E K E N C E «Dovarp, S. H. aud Devare, H. (t., I%4, Phyx. Kev., 183, No. 3B. B56S.(loldhabor M. and Hill, H. 1).» 1952, Itevs, Modmi 24, 179.Hoogenboom, A. M., 195S, Nuclear Instruments and Methods, 3, 57.Nuclear Data Sheets, Nat ional Academy of ScitiUceH, National Research Council, Wash­ington Ih C-. (1904)Hose, M. E., 1953, Phys. Rev,, 91, 010.Silvorberg, Lars, 1961. Arkiv Fysik, 20, 341.Stanford, A. L. and Rivers, W. K., .Ir., 1959, Revs, Scientific Instruments, 30, 719.

Gamma-Gamma Angular Correlation in Sn125

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/2517/1/Gamma-Gamma%20Angular%20Correlation%20_%20A.K.Nigam.pdf

Gamma-Gamma Angular Correlation in Sn125

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