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 $\gamma -\gamma$ and $\beta -\gamma$ coincidence, and multispectrum modes. Two groups of gamma rays with slightly different half-lives are observed in ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}_{}^m{}_{}{}^{}\left({\frac{9}{2}}^{+}\right)$ to decay to high spin levels with a half-life of 121±3 sec, and ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}_{}^g{}_{}{}^{}\left({\frac{3}{2}}^{+}\right)$ to low spin levels with 136±3 sec half-life. The decay energy of ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}_{}^g{}_{}{}^{}\to {}_{}{}^{121}{}_{}{}^{}\mathrm{Xe}_{}^g{}_{}{}^{}$ was measured to be 5.40±0.02 MeV and that of ${}_{}{}^{123}{}_{}{}^{}\mathrm{Cs}$(365±4 sec) to be 4.0±0.1 MeV. $K$-conversion coefficients determined by the $\frac{\mathrm{x}}{\gamma }$ method are 11±1 for the 38.38 keV transition of ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}_{}^m{}_{}{}^{}$, and 1.3±0.1 and 0.9±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 ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}_{}^m{}_{}{}^{}\left({\frac{9}{2}}^{+}\right)$, ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}_{}^g{}_{}{}^{}\left({\frac{3}{2}}^{+}\right)$, and ${}_{}{}^{123}{}_{}{}^{}\mathrm{Cs}$(${\mathrm{½}}^{+}$) 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 $\beta =+0.16\mathrm{} \mathrm{to} +0.19\mathrm{}$.

RADIOACTIVITY ${}_{}{}^{124}{}_{}{}^{}\mathrm{Xe}$($p$,$2n$)${}_{}{}^{123}{}_{}{}^{}\mathrm{Cs}$, $E_p=33\mathrm{}$ MeV; ${}_{}{}^{124}{}_{}{}^{}\mathrm{Xe}$($p$,$4n$)${}_{}{}^{121}{}_{}{}^{}\mathrm{Cs}$, $E_p=52\mathrm{}$ MeV; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coincidence, ICC, $Q_{\mathrm{EC}}$; deduced ${}_{}{}^{121}{}_{}{}^{}\mathrm{Xe}$, ${}_{}{}^{123}{}_{}{}^{}\mathrm{Xe}$ levels, $log\mathrm{ft}$, $I$, $\pi$; enriched Xe gas targets. In-beam ${}_{}{}^{122}{}_{}{}^{}\mathrm{Te}$($\alpha$,$5n\gamma$)${}_{}{}^{121}{}_{}{}^{}\mathrm{Xe}$, $E_{\propto }=69\mathrm{}$ MeV, $\gamma -\gamma$ coincidence, enriched Te targets.

• Received 16 March 1981

DOI:https://doi.org/10.1103/PhysRevC.24.1615