Deformation-dependent inner pockets in repulsive-core double-folding potentials for α decay of even–even heavy nuclei

Abstract

We develop a repulsive-core double-folding (DF+rep) model for the  decays of ¹⁹⁶Rn, ²⁰²Ra, ²²⁴Th, and ²²⁸U. Axial deformation of the daughter nucleus is included in both the radius and diffuseness of the Woods–Saxon density. Different deformation configurations are compared to separate the effects of quadrupole and hexadecapole deformation on the inner pocket, Coulomb barrier, and Wentzel–Kramers–Brillouin (WKB) tunneling integral. The repulsive-core term removes the unphysically deep attraction of the pure double-folding (DF) potential and produces a finite pocket in the density-overlap region. For oblate daughter nuclei with small , diffuseness deformation gives the main change in the potential and half-life, whereas the hexadecapole term becomes more important for prolate daughters. The full –  configuration gives the closest agreement with experiment in all four cases, showing that deformation should be included consistently in both the radius and diffuseness. Since  is fitted separately for each nucleus, however, this agreement reflects the ability of the repulsive-core parameter to account for short-range effects rather than an independent test of predictive power. These results show the combined role of surface deformation and short-range repulsion in -barrier tunneling.