Decay of Cs m , g 121 and Cs 123

Radiations from $^{121}\mathrm{Cs}^{m,g}$ and $^{123}\mathrm{Cs}$, produced by bombarding 41% enriched $^{124}\mathrm{Xe}$ gas targets with protons, have been investigated with several Ge detectors in singles, two parameter $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ and $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ coincidence, and multispectrum modes. Two groups of gamma rays with slightly different half-lives are observed in $^{121}\mathrm{Cs}^{m}({\frac{9}{2}}^{+})$ to decay to high spin levels with a half-life of 121\ifmmode\pm\else\textpm\fi{}3 sec, and $^{121}\mathrm{Cs}^{g}({\frac{3}{2}}^{+})$ to low spin levels with 136\ifmmode\pm\else\textpm\fi{}3 sec half-life. The decay energy of $^{121}\mathrm{Cs}^{g}\ensuremath{\rightarrow}^{121}\mathrm{Xe}^{g}$ was measured to be 5.40\ifmmode\pm\else\textpm\fi{}0.02 MeV and that of $^{123}\mathrm{Cs}$(365\ifmmode\pm\else\textpm\fi{}4 sec) to be 4.0\ifmmode\pm\else\textpm\fi{}0.1 MeV. $K$-conversion coefficients determined by the $\frac{\mathrm{x}}{\ensuremath{\gamma}}$ method are 11\ifmmode\pm\else\textpm\fi{}1 for the 38.38 keV transition of $^{121}\mathrm{Cs}^{m}$, and 1.3\ifmmode\pm\else\textpm\fi{}0.1 and 0.9\ifmmode\pm\else\textpm\fi{}0.1 for the 83.38 and 97.39 keV transitions of $^{123}\mathrm{Cs}$, requiring these transitions to be $40% M1+60% E2$, $90% M1+10% E2$, and $80% M1+20% E2$, respectively. The $log\mathrm{ft}$ values, the above multipolarities, and the branchings of electromagnetic transitions enable a few spin and parity assignments to levels in $^{121}\mathrm{Xe}$ and $^{123}\mathrm{Xe}$. Decay schemes of $^{121}\mathrm{Cs}^{m}({\frac{9}{2}}^{+})$, $^{121}\mathrm{Cs}^{g}({\frac{3}{2}}^{+})$, and $^{123}\mathrm{Cs}$(${\mathrm{\textonehalf{}}}^{+}$) are deduced from these observations. Some of the levels of $^{121}\mathrm{Xe}$ and $^{123}\mathrm{Xe}$ can be identified with low lying excitations of intrinsic states of the Nilsson model with deformation parameter $\ensuremath{\beta}=+0.16 \mathrm{to} +0.19$.