Cross-shell excitations near the "island of inversion": Structure of Mg-30

Excited states in Mg30 have been populated to ~6ℏ and 5 MeV excitation energy with the C14(O18,2p) reaction. Firm spin assignments for states with J>2ℏ have been made in this nucleus. The level scheme is compared to shell-model calculations using the Universal sd effective interaction and the Monte Carlo shell model method. Calculations employing a full sd model space fail to reproduce the observed levels. The results indicate that excitations across the N=20 gap are required at relatively low excitation energy to achieve a description of the data. The incorporation of the f7/2 and p3/2 orbitals into the model space gives improved results but indicate the need for further refinement of the models to reproduce the observed spectra.