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 defor med nuclei is constructed in order to study the role of particles in t he unique parity orbitals of heavy deformed nuclei and to test the val idity and applicability of some commonly used truncation procedures. W orking in a truncation-free environment and including quadrupole-quadr upole, spin-orbit, orbit-orbit, and pairing forces, we find that for s tandard nuclear systems the correlations generated among particles in the unique parity space and by the interaction of nucleons in the norm al parity orbitals with those in the unique parity orbitals play an im portant role in driving the many-particle system towards its maximum a llowed deformation. The results suggest that nucleons in the unique pa rity levels contribute significantly to the overall collectivity of a nuclear system and should be taken into account explicitly whenever po ssible, or at least through renormalization procedures that can be jus tified in special cases, like for collective states below the backbend ing region.