Observation of octupole excitations in $^{141}$Cs and $^{143}$Cs nuclei
Résumé
Excited states in $^{141}$Cs, populated in spontaneous fission of $^{248}$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 $^{141}$Cs and $^{143}$Cs nuclei. The new data for $^{141,143}$Cs do not support theoretical predictions of octupole deformation in the neutron-rich Cs isotopes and indicates octupole correlations weaker than observed in the corresponding Ba isotones.