Isomers and oblate rotation in Pt isotopes: Delineating the limit for collectivity at high spins

Rotation-aligned isomeric states and associated oblate collective sequences are established in even Pt isotopes. Reduced E2 transition probabilities for the deexcitation of the 12(+) isomers indicate an abrupt and unexpected quenching of oblate collectivity around neutron number N = 120. Structure and shape evolution at high spin in the heaviest stable isotopes is found to be markedly different from observations in the lighter ones. (C) 2015 The Authors. Published by Elsevier B.V.