Electromagnetic moments of exotic Na isotopes and their relation to the N = 20 shell gap

Abstract

The role of N = 20 shell-gap energy of unstable nuclei in the disappearance of the magic structure is investigated by calculating electromagnetic moments of Na isotopes with the Monte Carlo shell model. Comparison between the calculational and the experimental moments shows that the disappearance for Na isotopes should occur already at N = 19. It does not take place unless the spherical N = 20 shell gap of Na isotopes is much narrower than that of stable nuclei, which supports the mechanism of the disappearance originating from the spin-isospin dependence of the NN interaction.