THE EFFECT OF THE Z= 56 SUBSHELL ON INTERACTING BOSON MODEL (IBM)CALCULATIONS

The predictions of the exact O(6) symmetry limit of interacting boson model are reviewed for the Sn-Gd region. Evidence of the transition from O(6) to O(6)-SU(5) dynamical symmetry for the deformed nuclei in the 50≤ Z ≤ 64 region is discussed. In this research proposed a new scheme for IBM calculations near Z=56 which involves a drastic change in the proton boson number is critically examined. It is shown that this scheme is in agreement with the experimental trends observed for the B(E2;2 (1)(+) - 0(1)(+) transition probability. Energy levels and B(E2) are compared with IBM calculations assuming either a single Z= 50 - 64 shell or a subshell at Z=56. The present calculation improves agreement with experiment.