Decay-Scheme Studies ofXe125andXe127

Abstract

High-resolution conversion-electron studies have been made of the ${}_{}{}^{125}{}_{}{}^{}\mathrm{Xe}$ and ${}_{}{}^{127}{}_{}{}^{}\mathrm{Xe}$ decay schemes. The energies in KeV and multipolarities of the transitions seen in ${}_{}{}^{125}{}_{}{}^{}\mathrm{I}$ are 54.960±0.015, $M1+(0.05\mathrm{}\pm 0.03)\%E2$; 74.86±0.02, $E2+<\mathrm{}15\%M1\mathrm{}$; 113.57±0.03, $M1+(1.4\mathrm{}\pm 0.4)\%E2$; 188.43±0.03, $M1+(11.3\mathrm{}\pm 0.5)\%E2$; 210.43±0.04; 243.40±0.04, $E2+<\mathrm{}4\%M1\mathrm{}$; 372.08±0.06 and 453.83±0.05; while those in ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$ are 57.60±0.02, $M1+(0.7\mathrm{}\pm 0.1)\%E2$; 145.22±0.03, $E2+<\mathrm{}25\%M1\mathrm{}$; 172.10±0.03, $M1+<\%E2\mathrm{}$; 202.84±0.03, $M1+(21\mathrm{}\pm 3)\%E2$; and 374.96±0.05, $E2+<\mathrm{}30\%M1\mathrm{}$. The $\gamma$ rays associated with the ${}_{}{}^{125}{}_{}{}^{}\mathrm{Xe}$ decay have been studied using (NaI(Tl)-NaI(Tl) coincidence techniques and Ge(Li) $\gamma$-ray spectrometers. Transitions of energies 511, 553.9, 635.8, 717.1, 726.8, 809.4, 819.3, 846.5, 901.5, 937.3, 992.5, 1007.5, 1021.5, 1075.3, 1089.9, 1108.5, 1138.4, 1181.0, 1193.6, 1253.6, 1318.3, 1327.9, 1383.7, 1442.1, and 1560.4 keV are seen in addition to the ones observed in internal conversion. Angular-correlation measurements verify that the 511-keV quanta result from positron annihilation. A ${}_{}{}^{125}{}_{}{}^{}\mathrm{I}$ level scheme is given which accounts for all transitions. The $\gamma 54.960-\gamma 188.43$ and $\gamma 54.960-e_{K}188.43$ angular correlations have been measured. The correlation results together with the measured transition multipolarities are consistent only with respective spin values of $\frac{3}{2}$ and ½ for the 188.43- and 243.40-keV levels in ${}_{}{}^{125}{}_{}{}^{}\mathrm{I}$.