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 E 2 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. [ABSTRACT FROM AUTHOR]