Rotational band structure in 75Se

The high-spin states of 75Se have been investigated using the 59Co (19F, 2pn) reaction at 55 MeV. The positive-parity band has been extended to Iπ=29/2+ and the unfavored signature has been identified. The negative-parity band has been extended to Iπ=19/2- and band crossings were observed for the first time in both bands. Eleven new lifetimes were measured using the Doppler-shift attenuation method which allowed for extraction of transition strengths and transition quadrupole moments. The B(M1) strengths exhibit a staggering dependent on the signature splitting. Calculations based on the Woods-Saxon-Bogolyubov cranking model explain the signature-dependent alignment process in the g9/2 bands and predict signature inversion in all bands at high rotational frequencies. It is argued that the data are consistent with the transition from triaxial shapes with γ∼-30 degree, characteristic of one-quasiparticle configurations, to triaxial shapes with γ∼30 degree, characteristic of a three-quasiparticle configuration containing one aligned pair of g9/2 protons