Rotation-aligned isomer and oblate collectivity in Pt 196

An oblate rotational sequence, built on an aligned, two-quasineutron isomeric state has been established in Pt-196. The isomer has a half-life of 7.7(7) ns and is associated with the I-pi = 12(+), (i(13/2))(2) neutron configuration. Excited states, with angular momentum generated primarily through successive nucleon alignments, have been populated through 1p transfer from Au-197. The nucleus Pt-196 is the most neutron-rich Pt isotope for which high-spin states, beyond the 12(+) isomeric state, have been established thus far. Cranked shell model calculations have been performed to understand shape evolution with spin, and the role of nucleons occupying specific Nilsson orbitals in generating aligned angular momentum for both prolate and oblate deformations has been explored.