Analysis of α-decay widths of light 4 n nuclei

Abstract

Previous analyses of the α-widths of the ground state band of 20Ne are extended to most data for 20Ne, 16O, and 12C. The simple prescription that the spectroscopic factor is the ratio of the observed width to the single particle width calculated by a Woods-Saxon potential, is re-examined using R-matrix theory. Especially, the effects of antisymmetrization, the energy shift correction, and the energy dependence of the hard sphere scattering phase shift are taken into account. For narrow resonances the simple prescription gives good results, while for broad resonances the two latter effects are found important. We obtained a new formula for the spectroscopic factor which depends on the choice of the channel radius. The optimum value of the channel radius is also discussed. For levels whose nature is well known, we obtained generally good agreement with shell model predictions. For levels whose nature is not well known, the extracted spectroscopic factors are used to identify the band structure.