Multiparticle-multihole states in31Mg and33Mg: A critical evaluation

Abstract

The experiments that provide information about the level structure of the ``island of inversion'' isotopes ${}^{31}$Mg and ${}^{33}$Mg are reviewed. Since the model-independent measurement of their ground-state spins was done, much experimental data can be reinterpreted, and spins and parities can be assigned to their excited states. Both experimental level schemes are found in very good agreement with calculations based on antisymmetrized molecular dynamics combined with the generator coordinate method. These calculations predict that both ground states are dominated by $2\ensuremath{\hbar}\ensuremath{\omega}$ neutron excitations (more than 85$%$ of the wave function). In the case of ${}^{33}$Mg, the energy of the $1\ensuremath{\hbar}\ensuremath{\omega}$ and $3\ensuremath{\hbar}\ensuremath{\omega}$ levels are calculated about 400 keV too high with respect to the ground state, while in ${}^{31}$Mg the $1\ensuremath{\hbar}\ensuremath{\omega}$ levels are calculated only 200 keV too high. New key experiments are suggested.