Pande, U S

Singh, B P

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In d ia n  J ,  PJi/ya, 49, 350»>!}64 (1975)Gamma-gamma-gamma angular correlation method for the study o f the cascade 589-296-316 kev inU. S. P and e  and  B . P. S ingh  Department of Physics, University of Boorkee, Roorkee, U.P,{Received 2 January 1975)Throe Nal(Tl) detectors (Sj>ectrometers) mounted in the plane of the table (two detectors are fixed perpendicular to each other and third detector is movable in the opposite quadrant of the two fixed detec­tors) aie used for the coincidence and angular correlation studies for the triple gamma cascade 589 keV->296 keV—> 316 koV in Pt^ ®^  from the decay of The method of tirple angular correlation isdescribed and multipolarity of the 296 keV transition is determined.1. I ntroductionThe gamma-gamma directional correlation in the decay of Ir^ ®‘- has been studied by many workers. Khan et at (1969) and Hirshfold & Hoppes (1970) studied it with the aim of the determination of transition mixing ratios for various gamma transitions. Energies of the gamma-rays of 296 keV, 308 keV and 316 keV arc very close and also energies of gamma-rays of 589 keV, 604 keV and 612 keV arc close. Therefore, large correction or extrapolation is needed for the interpretation of the results in angular correlation studios even using Ge(Li) detectors. In order to overcome those difficulties an attempt has been made to study the angular cor­relation of the cascade of three gamma-rays i.e., 589 kcV-296 ke4V-3l6 keV inPtioa,2. E xperim entalThere are two simple geometrical considerations for the mounting of the three detectors foi‘ triple angular correlation studies.(1 ) When all the throe detectors are in one plane (i.e., in the plane of the tabl(^) two of the detectors are fixed perpendicular to each other and the third detector is movable and can be kept at various angles. Lt t^ us call it P  geometry.(2) When two of the detectors arc in tlie plane of table (one of them is mov­able) and the third detector is perpendicular to the plane of the table* Lot us call it C geometx’y.If the throe gamma-rays are of different energies then, it is simple to choose them in photopeaks in three different detectors but if the throe gamma rays are of the same energies, then we can look for a proper geometry of the mounting of the detectors,360Angular correlation method for the cascade 351Wh©n all the three gamma rays are of same energies then angular correlation ia is(jtropio in the geometrical mounting P  but is not so in the geometricpil mount­ing G. (the details are given by Singh ei al (1971)). Therefore, the geomctrioal m ounting G was taken for the angular correlation studies in this case.Now two gamma-rays are of almost the same energies and the third one of different energy as it is taken for this study, of the cascade of 689 keV-296 keV- :U0 keV in Pt^ ®^ . The triplet gamma angular correlation coefficients were cal­culated for the P  and G geometry by method given earlier (Singh et al 1971, 1972). If we take all the three gamma rays to be pure Pg with spin sequence 4->2 ->2->0, tho angular correlation coefficients are as follows :(i) P  geometry of the mounting of detectos mentioned above=  -0.182, =  0.2471,(ii) G geometry of the mounting of detectors as mentioned aboveA^ =  -0.0493, A^ =  0.0006.The anisotropy is much large in geometrical mounting P  compared to geometrical mounting G. Therefore, in this case geometrical mounting P  is preferred. In this geometry of the mounting the 689 keV gamma rays is detected by the detectoi* marked I as given in figure 1 and other two detectors marked II  and I II  are as­signed to detect both 296 and 316 keV gamma rays. Therefore two considera­tions are possible.1. The arrangement of detectors. Detector marked I  and II are fixed and detector maked III Is movable for the angular correlation studies. Detector marked I detects the 589 keV gamma ray and other two detectors (II and III) detect the gamma rays at 300 keV in 4 volts channel width.(a) When 296 keV is detected by detector marked II  and 316 keV is detected by tho detector marked I I I  which is movable making an angle 6 with the detector marked I shown in figure 1.(b) When 316 keV is detected by detector marked II  and 296 keV is detected by the detector marked H I the movfible detector,352 U. S. Pande and B. P. SinghBoth the Bituations are equally probable therefore the average of the twois to be taken.Fig. 2. Triple gamma coincidenco spoctrurn along with a single spectrum after subtract­ing the chance counting rate.Fig. 2. Plot of A s  versus Q. Curve A"' is for the geometry when 3H»koV gamma-ray is detected in movable detector and other gamma-rays in fixed detectors and curve A '  is for tho geometry when 296 keV gamma-ray is detected in movable detector and other gamma-raya in fixed detectors. Curve A  is for mean of the two geometries.The details of the experimental setup is described earlier (Singh ei al 1971, 1972). Triple coincidence spectrum is given in figure 2 which is taken selectingAngular correlation method for the cascade 353rramma-rays at the photopeak in two detector (spectrometerR) at 300 keV in 4 volts (1 volt =  15keV) channel width for gamma-gamma coincidence gate and scanning the spectrum in other detector (spectrometer) for triple gamma-ray coincidence spectrum. The detector detecting 589 keV at the plxotopeak in 4 volts channel width and one of the detector detecting gamma-rays at the photo- p(uik of 300 keV in 4 volts channel width are fixed perpendicular to each other and other detector detecting gamma ray in 4 volts channel width is movable in opposite quadrant in the interval of 22.5'’ for angular correlation studios. The W(0) is obtained by the method of least square fit. The solid angle correction is not applied. This correction is included in the theoretical calculation. The W(0) is as follows :W{d) =  1 - ( 0 . 1 1 ± 0 . 0 2 1 ) P 2 ( c o s  ( 9 ) + ( 0 . 0 6 2 ± 0 . 0 3 ) P 4 ( c o s  6)Considering the spin for the cascadeand considering both 589 and 316keV transition to bo pure the mixture of dipole and quadruple in 296 keV is determined. This is done by plotting (which is given in figure 3) the angular correlation coefficient versus Q(Q =  where 8 is amplitude mixing ratio.The experimental value of ^2 moan curve giving =  0.005t§:8o§5Q = 0 . 9 9 0 i { { d  >  0. is rejected as 296 keV is predominantly E^ transi­tion. is accepted which gives 8 =  + 10l|(Biedenharn & Rose 1953)convention lias been followed. Results of 8 by different workers are displayed by Hirshfeld Hoppes (1970). Our value lies in the same range but with opposite sign. The oj)p(>sito sign of 8 has been obtained by (Ofer 1959) for the middle gamma-ray of the cascade of three gamma-rays when angular corelation of the first and second gamma-rays and angular correlation of the second and third gamma-rays are done. Therefore we should get (—) sign (or pliase) in triple gamma-rays angular con elation due to phase convention of Biedenharn & Rose (1953). Therefore tlu^  actiial sign of 8 shall be positive (or negative) if the experimental value is nega­tive (or positive). Therefore, the sign of 8 in this study is also (—) and therefore lOti.A0SKOm.SOOMENTWe are thankful to  D epartm ent o f Atom ic Energy, G overnm ent o f India for the financial support for th is project,354 U. S. Pande and B. P. SinghB b f u b b n o b sB iod on h arn  L . C. & H obc M . E . 1963 Jiev. M od. P h ys. 2 5 , 7 2 9 , Hii'Bhfold A . T . &  H o p p e s  D . D . 1970  Phya. Rev. C 2 , 2341 . K h a n  M. Y . et al 1969  Phya Rev. 182 , 1259.O fer S . 1969  Phya. Rev. 111 . 870.S in gh  B . P . et al 1971 Phya. Rev. C 4. 1610.S in g h  B . P . al 1972 Phya. Rev. C6, 1789.

Gamma-gamma-gamma Angular Correlation Method for the Study of the Cascade 589-296-316 Kev in Pt 192

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Gamma-gamma-gamma Angular Correlation Method for the Study of the Cascade 589-296-316 Kev in Pt 192

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