Band crossings in the positive-parity high-spin states of ⁸³Rb and ⁸⁵Y

Positive-parity high-spin states in the odd-proton nuclei ⁸³Rb and ⁸⁵Y have been populated via the ⁶⁸Zn(¹⁸O,p2n) reaction at 56 MeV and the ⁵⁹Co(²⁸Si,2p) reaction at 99 MeV up to (37/2⁺) and (33/2⁺), respectively. In both nuclei band crossings have been observed at a spin of 21/2 and interpreted as resulting from the alignment of a g_9/2 neutron pair, as in other odd-proton nuclei with 46 neutrons. In the three-quasiparticle high-spin excitations, the observed signature splitting and total Routhian surface calculations indicate that the ⁸³Rb nucleus exhibits a well-deformed near-oblate shape. No second alignment has been observed in the yrast sequence of ⁸³Rb up to a rotational frequency of 0.95 MeV, indicating that for Z = 37 and an oblate shape the breaking of a g_9/2 proton pair is energetically expensive.