Periodic-orbit approach to nuclear shell structures with power-law potential models: Bridge orbits and prolate-oblate asymmetry

摘要

Deformed shell structures in nuclear mean-field potentials are systematically investigated as functions ofndeformation and surface diffuseness. As the mean-field model to investigate nuclear shell structures in a widenrange of mass numbers, we propose the radial power-law potential model, V ∝ rα, which enables a simplensemiclassical analysis by the use of its scaling property. We find that remarkable shell structures emerge atncertain combinations of deformation and diffuseness parameters, and they are closely related to the periodic-orbitnbifurcations. In particular, significant roles of the “bridge orbit bifurcations” for normal and superdeformed shellnstructures are pointed out. It is shown that the prolate-oblate asymmetry in deformed shell structures is clearlynunderstood from the contribution of the bridge orbit to the semiclassical level density. The roles of bridge orbitnbifurcations in the emergence of superdeformed shell structures are also discussed.