Excited states in ${}^{142}\mathrm{Cs}$ and ${}^{144}\mathrm{Cs}$, populated in the spontaneous fission of ${}^{248}\mathrm{Cm}$ and ${}^{252}\mathrm{Cf}$ and in thermal neutron-induced fission of ${}^{235}\mathrm{U}$ and ${}^{242}\mathrm{Am}$ were studied by means of $\gamma$ spectroscopy using the EUROGAM2 and Gammasphere multidetector Ge arrays and the LOHENGRIN fission-fragment separator, respectively. In ${}^{142}\mathrm{Cs}$, a band and an isomer with a half-life of $T_{1/2}=11(3)$ ns have been identified. Spins and parities have been proposed for excited levels in this nucleus. In ${}^{144}\mathrm{Cs}$ excited levels have been observed. A $T_{1/2}=1.1(1)$ $\mu$s isomer was found with a $\gamma$ cascade, which probably feeds this isomer. There is also an indication of a nanosecond isomer in ${}^{144}\mathrm{Cs}$. Quasiparticle-rotor model calculations done in this work allowed proton-neutron configurations to be proposed for levels in ${}^{142}\mathrm{Cs}$ and ${}^{144}\mathrm{Cs}$.

• Received 18 October 2009

DOI:https://doi.org/10.1103/PhysRevC.80.064317