Several rotational bands have been populated in the Z=55 nucleus ${}_{}{}^{125}{}_{}{}^{}\mathrm{Cs}$ using the fusion evaporation reaction ${}_{}{}^{110}{}_{}{}^{}\mathrm{Pd}$${(}^{19}$F,4n), at a beam energy of 74 MeV. The resultant γ rays were detected using standard γ-ray spectroscopic techniques with an array of six Compton-suppressed Ge detectors and a fourteen-element bismuth-germanate ball. The low-lying yrast structure is found to be dominated by the unique parity π${\mathit{h}}_{11/2}$ orbital, manifest as a decoupled band with a large signature splitting. A crossing occurs in this band at ħ${\mathrm{\omega }}_{\mathit{c}}$=0.42 MeV, which is interpreted as [ν${\mathit{h}}_{11/2}$${]}^2$ pair alignment. In addition, a strongly coupled negative-parity structure with large B(M1)/B(E2) ratios is observed feeding both signatures of the π${\mathit{h}}_{11/2}$ band. Bands built on the normal-parity π${\mathit{g}}_{7/2}$ and π${\mathit{g}}_{9/2}^{\mathrm{-}1}$ orbitals have also been confirmed and extended. These structures are compared to cranked-shell-model calculations and the systematics of the region.

• Received 15 August 1991

DOI:https://doi.org/10.1103/PhysRevC.44.2390