Relationship between the fermion dynamical symmetric model Hamiltonian andnuclear collective motion - art. no. 024322

In this paper we investigate the role of single-particle energies on the lo w-lying states of Ba-132, a typical O(6) nucleus in the IBM and the fermion dynamical symmetric model (FDSM). It is found that one can reproduce the p hysical quantities of a realistic system with nondegenerate single-particle energies using degenerate single-particle levels and a slightly different parametrization of the two-body interaction. However, if the single-particl e splittings are enlarged by a factor of 1.5, the O(6)-like behavior of the nucleus is lost and a model that assumes degenerate levels cannot describe its collective structure. Contributions from interactions other than monop ole and quadrupole pairing and a quadrupole-quadrupole force are found to b e unimportant. Although the role of the abnormal-parity level depends on th e details of the single-particle structure, its effects can be "compensated " by using different Hamiltonian parameters and degenerate single-particle levels in a FDSM treatment.