Breaking of the neutron magic number N=20 in 32Mg and 30Ne and its possible relation to the cluster structure

The neutron-rich nuclei Mg-32 and Ne-30 are studied using a new version of antisymmetrized molecular dynamics (AMD). Due to the use of a deformed Gaussian as the single particle wave packet, the description of the deformation properties of Mg isotopes is drastically improved, and l . s force is accounted for more largely and sufficiently. After the angular momentum projection, Mg-32 and Ne-30 have deformed ground states, and the experimental data for Mg-32 are reproduced with reasonable accuracy. The deformation of the mean field is found to be essential to describe these nuclei. The ground states of these nuclei have neutron 2p2h structure. In Ne-30, the cluster-like and the mean-field-like structures coexist. The ground state of 32Mg has a mean-field-like structure. In the vicinity of the ground state, this nucleus is expected to have excited status with cluster-like structure-that possesses the neutron 4p4h configuration.