0 D ec 1 99 9 Partial Dynamical SU ( 3 ) Symmetry and the Nature of the Lowest K = 0 Collective Excitation in Deformed Nuclei

We discuss the implications of partial dynamical SU(3) symmetry (PDS) for the structure of the lowest K=0 + (K = 0 2) collective excitation in deformed nuclei. We consider an interacting boson model Hamiltonian whose ground and γ bands have good SU(3) symmetry while the K = 0 2 band is mixed. It is shown that the double-phonon components in the K = 0 2 wave function arise from SU(3) admixtures which, in turn, can be determined from absolute E2 rates connecting the K = 0 2 and ground bands. An explicit expression is derived for these admixtures in terms of the ratio of K = 0 2 and γ bandhead energies. The SU(3) PDS predictions are compared with existing data and with broken-SU(3) calculations for 168 Er.