Gamma-gamma directional correlation measurements in192Os

Abstract

Abstract. E 2/M 1 mixing ratios of transitions in 192Os have been determined by the gammagamma directional correlation technique. The results are: 6(484.5 keV)= -10_+ l, 6(283.3keV)=-3.8+0.7 and 6(201.3keV)=-4.6_+l.The even nuclei in the osmium region have been the subject of many theoretical and experimental investigations. The most extensive theoretical calculations have been performed by Kumar and Baranger by use of the pairing-plus-quadrupole model [1]. Detailed nuclear properties are predicted, the E2/M1 mixing ratios of gamma transitions between low lying states are given with both magnitude and relative phase between the reduced E2 and M1 matrix elements, which enables a detailed comparison with experimental data. In the present paper a determination of three E2/M1 mixing ratios in 192Os is reported. During the course of this work, Helppi et al. [2] published results concerning the same isotope. However, the experimental methods employed as well as the ways of extracting the information are slightly different. Furthermore, in the present work the mixing ratio of the 283.3 keV transition is for the first time determined by the gamma-gamma directional correlation method. It was therefore felt that the present report could complement the available experimental data and increase their significance. The source, 192Ir, as IrC1 in dilute HCI solution, was delivered by the Radiochemical Centre, Amersham. The gamma-gamma directional correlation measurements were performed with a multidetector system [3], utilizing 6 NaI(T1) detectors [38 mm(dia) x 50 mm] and 2 Ge(Li) detectors (90 cm 3, 12 ~o eft. 2.7 keV resolution and 55 cm 3, 8.5 ~o eft. 2.4 keV resolution). Twelve coincident Ge(Li) energy spectra were simultaneously recorded. Only a small change was made as compared to the system described in Ref. 3, concerning the addition of the two energy signals of the Ge(Li) detectors. Here two biased amplifiers were connected into the system after the two main amplifiers in order to avoid the energy deterioration in the stored spectra due to noise summation. Thus the individual energy resolutions of the Ge(Li) detectors could be maintained in the measurements. The directional correlation coefficients of the following cascades were determined (cf. the decay scheme, Fig. 1

Study of the radioactive decay of192Ir

“…In case of 192Os, the present value for the mixing ratio of 201 and 283 keV transition are in general agreement with those obtained by other workers [18,22]. The present mixing ratio value of 485 keV is in good agreement with the value deduced from nuclear …”

“…The present measured directional correlation coefficients for 9 cascades in 192pt and 4 cascades in 191Os alongwith the results by earlier workers [17][18][19][20][21][22] are presented in Table 3. The better energy resolution of the HPGe detectors does not necessitate any correction for the interference caused from unwanted cascades in case of 296-316, 589-296, 308-296, 308-316, 589-316 and 283-206 keV angular correlation measurements.…”

“…The directional correlation measurements of 9 cascades in 192pt and 4 cascades in ~92Os have been performed by using a HPGe-HPGe detector set up with much better energy and time resolution than used in previous measurements [17][18][19][20][21][22] …”