Superdeformation in the Hg-Pb region and an extension of IBM

The superdeformation in the Hg-Pb region is investigated on the basis of the Nilsson + particle-number-conserving BCS model and the Interacting Boson Model. The basic structure of the superdeformed states is studied especially from the viewpoint of the collective nucleon pairs. Significant differences are found in the structure of collective pairs between the cases of the normal and the superdeformed states. The Interacting Boson Model is extended to describe the superdeformation. A phenomenological Hamiltonian is presented and applied to clarify the stabilization mechanisms and the spin dependent properties of the superdeformed states. It is shown that the unified description of two different configurations, normal low-lying states and the superdeformed states can be made within this framework. Systematic description of dynamic moment of inertia is given by considering the effects of quadrupole parameters. (author). 76 refs