Properties of shape-driving orbitals: Rotational bands inLa131

Several rotational bands have been populated in ${}_{}{}^{131}{}_{}{}^{}\mathrm{La}$ via the ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}$ ${(}^{19}$F, 4nγ) fusion-evaporation reaction. Bands built on low-lying $h_{11/2}$, $g_{7/2}$, and $d_{5/2}$ proton states have been identified. At higher spins, both proton and neutron [$h_{11/2}$ ${]}^2$ alignments have been observed. While the proton alignment from low-Ω orbitals maintains a prolate nuclear shape, the alignment of high-Ω neutrons drives the nucleus to a collectively rotating oblate shape (γ∼-60°). The results are interpreted in the framework of the cranked shell model. In addition, B(M1;I→I-1)/B(E2;I→I-2) ratios have been extracted for several of the bands and the results compared to a semiclassical model to identify the detailed structure.