Shell-model determination of the interacting boson model parameters for two nondegenerate j shells

The interacting boson model is examined from a microscopic viewpoint using the generalized seniority scheme. The present discussion focuses on regions of the periodic table in which the many nondegenerate nucleon orbits can be approximated in terms of two nondegenerate orbits, the sum of whose occupancies is chosen to be the same as the total occupancy of the major shell being studied. Predictions for the interacting boson model parameters are obtained by constructing the zeroth-order boson images of the corresponding fermion operators. Calculations are carried out for the tungsten isotopes, and the predicted interacting boson model parameters are found to be in good overall agreement with the empirically determined values for the tungsten isotopes. The calculations reproduce the observed SU(3) or rotational character of the low-lying energy states in the N = 96 to 114 mass region. NUCLEAR STRUCTURE Interacting boson model, microscopic determination of model parameters for two nondegenerate j shells. Use of theoretical parameters to predict experimental results for tungsten.