On the treatment of intruder levels in strongly deformed nuclei in the framework of the SU(3) shell model
A model system which mimics the shell-model dynamics of strongly deformed nuclei is constructed in order to study the role of particles in the unique parity orbitals of heavy deformed nuclei and to test the validity and applicability of some commonly used truncation procedures. Working in a truncation-free environment and including quadrupole-quadrupole, spin-orbit, orbit-orbit, and pairing forces, we find that for standard nuclear systems the correlations generated among particles in the unique parity space and by the interaction of nucleons in the normal parity orbitals with those in the unique parity orbitals play an important role in driving the many-particle system towards its maximum allowed deformation. The results suggest that nucleons in the unique parity levels contribute significantly to the overall collectivity of a nuclear system and should be taken into account explicitly whenever possible, or at least through renormalization procedures that can be justified in special cases, like for collective states below the backbending region. © 1995.