Woods-Saxon-Gaussian potential and alpha-cluster structures of alpha + closed shell nuclei**Supported by the National Natural Science Foundation of China (11535004, 11761161001, 11375086, 11120101005, 11175085, 11235001), the National Key R&D Program of China (2018YFA0404403, 2016YFE0129300) and the Science and Technology Development Fund of Macau (008/2017/AFJ)

Abstract

The Woods-Saxon-Gaussian (WSG) potential is proposed as a new phenomenological potential to systematically describe the level scheme, electromagnetic transitions, and alpha-decay half-lives of the alpha-cluster structures in various alpha + closed shell nuclei. It modifies the original Woods–Saxon (WS) potential with a shifted Gaussian factor centered at the nuclear surface. The free parameters in the WSG potential are determined by reproducing the correct level scheme of 212Po=208Pb+α. It is found that the resulting WSG potential matches the M3Y double-folding potential at the surface region and makes corrections to the inner part of the cluster-core potential. It was also determined that the WSG potential, with nearly identical parameters to that of 212Po (except for a rescaled radius), could also be used to describe alpha-cluster structures in 20Ne=16O+α and 44Ti=40Ca+α. In all three cases, the calculated values of the level schemes, electromagnetic transitions, and alpha-decay half-lives agree with the experimental data, which indicates that the WSG potential could indeed capture many important features of the alpha-cluster structures in alpha + closed shell nuclei. This study is a useful complement to the existing cluster-core potentials in literature. The Gaussian form factor centered at the nuclear surface might also help to improve our understanding of the alpha-cluster formation, which occurs in the same general region.