Identification of excited states in Cs-117: Systematics of the nu(h(11/12))(2) alignment - art. no. 024319

Excited states have been identified in the very neutron-deficient Cs-117(55 )62 nucleus. High-spin spectroscopy has been performed using the Gammaspher e array, and the assignment of gamma-ray transitions to Cs-117 has been mad e in a separate experiment in which gamma rays were detected in coincidence with x rays and with recoiling evaporation residues. A previously observed sequence of five gamma rays has been extended by 11 transitions, to high s pin, and has been identified as the yrast pi (h(11/2))[550]1/2(-) band of C s-117. Two additional bands have been observed and are tentatively assigned to be based on protons in the [404]9/2(+) and [422]3/2(+) orbitals. Alignm ents of pairs of h(11/2) neutrons and protons are observed in all of the ba nds. The alignments are compared to cranked Woods-Saxon calculations, and a re discussed with respect to the effects of a neutron-proton interaction. O f particular interest are the features of the nu (h(11/2))(2) alignment in the pi [550]1/2(-) band and of the pi (h(11/2))(2) alignment in the [422]3/ 2(+) band. The frequencies of these alignments can be qualitatively explain ed only if a neutron-proton interaction is taken into account.