Excited states in ${}^{145}\mathrm{Cs}$, populated following the spontaneous fission of ${}^{248}\mathrm{Cm}$, were studied by means of prompt-$\gamma$ spectroscopy, using the EUROGAM2 multidetector array. A new level scheme of ${}^{145}\mathrm{Cs}$ was proposed. We identified a decoupled band corresponding to $1/2[550]$ proton configuration and interpreted the ground-state band as a mixed configuration of $1/2[440]$ and $3/2[422]$ proton orbitals. Quasiparticle-rotor calculations performed for ${}^{145}\mathrm{Cs}$ support such assignments. The electric dipole moment in ${}^{145}\mathrm{Cs}$, $D_0=0.013(4)$ efm, is smaller than in lighter Cs isotopes, which suggests that octupole correlations in Cs isotopes decrease at the neutron number $N=90$, similarly as observed in the ${}^{146}\mathrm{Ba}$ and ${}^{147}\mathrm{La}$ isotones.

• Received 24 July 2009

DOI:https://doi.org/10.1103/PhysRevC.82.017301