The decays of ${}_{}{}^{141}{}_{}{}^{}\mathrm{Xe}$, ${}_{}{}^{140}{}_{}{}^{}\mathrm{Xe}$, and ${}_{}{}^{136}{}_{}{}^{}\mathrm{I}$ were examined for the presence of energy levels in ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{140}{}_{}{}^{}\mathrm{Cs}$, and ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$, respectively, with measurable half-lives in the nsec range. Using a least-squares fitting procedure to analyze the delayed coincidence data taken with a planar Ge(Li)-plastic scintillator system, the half-lives of the following levels were measured: ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$: 69.0 keV, 23.3 ± 0.7 nsec; 105.9 keV, 8.7 ± 0.2 nsec; ${}_{}{}^{140}{}_{}{}^{}\mathrm{Cs}$: 13.9 keV, 471 ± 51 nsec; 64.7 keV, 3.7 ± 0.3 nsec; 103.1 keV, 7.3 ± 0.3 nsec (average of two measurements). In addition, upper limits for the half-lives of other levels in these two isotopes are also given, as well as for some levels in ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$. Possible multipolarities of the transitions are discussed.

RADIOACTIVITY ${}_{}{}^{136}{}_{}{}^{}\mathrm{I}$, ${}_{}{}^{140}{}_{}{}^{}\mathrm{Xe}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Xe}$ from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n, f)$; measured delayed coin; deduced $T_{\frac{1}{2}}$ for levels in ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$, ${}_{}{}^{140}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$; Ge(Li) and scin detectors; mass-separated activities.

• Received 26 August 1974

DOI:https://doi.org/10.1103/PhysRevC.11.913