THE U(5)-O(6) MODEL - AN ANALYTICAL APPROACH TO SHAPE COEXISTENCE

A completely analytical model describing shape coexistence by mixing b etween the normal (U(5)) and the intruder (O(6)) configuration is prop osed. The model based on the IBM-1 provides analytical expressions for the energies and wavefunctions of a restricted number of levels, rele vant B(E2) values, rho(E0) values and quadrupole moments. It relies on the important selective mixing that occurs between normal and intrude r states governed by the O(5) symmetry. The analytical expressions of the B(E2) values allow a fit to the experimental data which takes into account global (spins and energies) and local (B(E2) values) properti es of the structure of the atomic nucleus making it possible to test t he model predictions in detail. In addition to the application of the model to Cd-110,Cd-112,Cd-114, some interesting effects of the O(5) gr oup, present in both dynamical symmetries involved in the configuratio n mixing, are discussed.