Shell model calculations for masses 27, 28 and 29: Specific application to 27, 28Mg and 28, 29Al

Abstract

A shell model calculation has been performed in a truncated 1 d 5 2 , 2 s 1 2 , 1 d 3 2 configuration space with a modified surface-delta-interaction Hamiltonian for the T = 1, 3 2 and 2 nuclei of A = 27–29. The parameters of the model Hamiltonian were obtained from a fit to experimental data from T = 0 and T = 1 2 nuclei of the same region. Excitation energies, single-nucleon spectroscopic factors, electric quadrupole moments and transition strengths and magnetic dipole moments and transition strengths were calculated. Decay properties of the T = 2 and T = 1 multiplets in A = 28 and the ΔT = 1, M1 transitions from T = 3 2 levels in A = 27 and 29 nuclei have been studied in particular. The results indicate that the present shell model is able to describe quantitatively the nuclear structure around mass 28 in a unified approach in a fashion similar to the excellent descriptions available in this same theoretical framework for lighter and heavier mass regions of the sd shell.