Shell-model calculations with an adjusted surface-delta interaction (I) application to spectroscopic factors inA=24–28 nuclei

Abstract

Shell-model calculations have been performed for positive-parity levels of theA=24–28,T≦3/2 nuclei in a 1d _5/22s _1/21d _3/2 configuration space. The space, for each (A, J, T) set, was restricted such that only mixing of less than about 300 low-lying pure configurations was allowed. An effective interaction (MSDI) was used of which the parameters have been determined by a fit of the calculated energies to the experimental values. This resulted in an averaged deviation of 0.52 MeV for 67 fitted levels. Spectroscopic factors have been calculated with the derived wave functions. In order to obtain better agreement for the energies, all of the 63 two-body matrix elements and three single-particle energies were adjusted systematically. The wave functions derived from this adjusted set of matrix elements denoted by ASDI yield considerably better spectroscopic factors. For comparison, the spectroscopic factors have also been calculated in a 1d _5/22s _1/2 model space. The omission of the 1d _3/2 subshell was found to result in a substantially poorer agreement for the spectroscopic factors for 1d _5/2 and 2s _1/2 transfer.