Shell-model calculations on A = 38 nuclei

Abstract

The shell model is used to investigate properties of levels in the A = 38 nuclei. An inert 28Si core with a residual two-particle interaction between the outer nucleons is assumed. The negative parity states are described by a closed 2 s 1 2 shell, five nucleons in the 1 d 3 2 shell and one nucleon in the 1 f 7 2 or 2 p 3 2 shell. For the positive parity states, all configurations in the 2 s case1 2 and 1 d 3 2 shell are taken into account. The effective two-particle interaction is chosen to be a modified surface delta interaction. The four parameters of this effective interaction are determined in a least-squares fit to the excitation energies of 15 nuclear levels. The rms deviation of the calculated energies from the experimental energies is 0.28 MeV. From the values of these parameters, the energies and wave functions of about 50 levels are derived. The wave functions are used to determine γ-ray branching ratios, mean lives, ƒt values in allowed β-decay and spectroscopic factors for the 37Cl(d, p) 38Cl reaction. The computed branching ratios, mean lives and ƒt values agree generally within a factor of 2.5 with the experimental values. Good agreement with experiment is obtained for the spectroscopic factors.