A method for truncating the nuclear shell model in terms of Nilsson orbits is developed and tested in the context of a simple model that admits coexistence between deformed and spherical configurations. The method reproduces the exact-diagonalization spectra of both the spherical and deformed configurations if angular momentum projection is carried out prior to diagonalization. Implementation of this method in m-scheme shell-model codes is discussed.

• Received 3 September 1992

DOI:https://doi.org/10.1103/PhysRevC.47.399