Evidence for Noncollective Oblate Structures at High Spin in Cs-123

High-spin states in Cs-123 were populated in the Ni-64(Ni-64,p4n) reaction at a beam energy of 265 MeV. Gamma-ray coincidences were measured using the Gammasphere spectrometer. Two additional bands have been placed in the level scheme and the four previously known bands have been extended to higher spin. At the highest spins, two of the bands show irregular level sequences. These structures of noncollective excitations, which compete with collective rotation, are interpreted as band-terminating states. The results are compared to cranked Nilsson-Strutinsky calculations, and configuration assignments to the bands and to the terminating states are discussed.