Excited states in ${}^{141}\mathrm{Cs}$ and ${}^{143}\mathrm{Cs}$, populated in spontaneous fission of ${}^{248}\mathrm{Cm}$, were studied by means of prompt-$\gamma$ spectroscopy, using the EUROGAM2 multidetector array. This work reports the first observation of octupole excitations in the ${}^{141}\mathrm{Cs}$ and ${}^{143}\mathrm{Cs}$ nuclei. The new data for ${}^{141,143}\mathrm{Cs}$ do not support theoretical predictions of octupole deformation in the neutron-rich $\text{Cs}$ isotopes and indicates octupole correlations weaker than observed in the corresponding $\text{Ba}$ isotones.

• Received 3 March 2003

DOI:https://doi.org/10.1103/PhysRevC.69.017305