Multiparticle-multihole states in Mg-31 and Mg-33: A critical evaluation

The experiments that provide information about the level structure of the "island of inversion" isotopes Mg-31 and Mg-33 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 (h) over bar omega neutron excitations (more than 85% of the wave function). In the case of Mg-33, the energy of the 1 (h) over bar omega and 3 (h) over bar omega levels are calculated about 400 keV too high with respect to the ground state, while in Mg-31 the 1 (h) over bar omega levels are calculated only 200 keV too high. New key experiments are suggested.status: publishe