Band crossing and the prealignment B(E2) anomaly in \u3csup\u3e126\u3c/sup\u3eBa

A theoretical interpretation of the reduction in E2 strengths in 126Ba prior to backbending is presented. A shell model basis is built from normal parity orbilals organized into multiplets of a pseudo SU(3) symmetry coupled to h 11 2 configurations restricted to states of seniority zero and two. Within the framework of the model the scattering of a pair of protons from normal parity to the h 11 2 orbital produces band crossing and a corresponding reduction in E2 transition strengths prior to pair alignment which is the principal mechanism of the backbending. © 1981