SPECTROSCOPY OF CS-123 - CONFIGURATION DEPENDENT CROSSING FREQUENCIES

Several collective structures have been populated in the Z = 55 nucleus 123Cs following the Pd-108(F-19,4n) fusion-evaporation reaction at a beam energy of 76 MeV. The low-lying structure is found to be dominated by a decoupled rotational band built on the unique-parity pi-h11/2 orbital. Rotational structures based on the normal-parity g7/2 proton and the g9/2 proton-hole orbitals are also observed. Rotational alignments occur in the pi-h11/2 band at hBAR-omega(c) almost-equal-to 0.44 MeV, and in the pi-g9/2(-1) band at hBAR-omega(c) = 0.38 MeV, both attributed to the rotational alignment of a pair of h11/2 neutrons, despite the different crossing frequency. In addition, the gamma-vibrational band built on the pi-h11/2 Orbital has been observed feeding both signatures of the corresponding rotational cascade. These results are compared to cranked shell model calculations and to the systematics of the region.