Speaker
Description
The island of inversion is a region in which their ground states are dominated by 2p–2h intruder configurations across a major shell gap rather than normal 0p–0h configurations. This behavior leads to the breakdown of magic numbers and plays an important role in understanding the shell evolution in neutron-rich nuclei. In particular, $^{32}$Al lies near the island of inversion and it is an important nucleus for studying the effect of interaction between normal and intruder configurations.
In this work, we performed shell-model calculation using the USD, USDB and SDPF-M interactions, which show some disagreement with experimental data such as the incorrect level ordering in $^{32}$Al and $^{26}$F. We specified the most sensitive matrix elements of shell-model Hamiltonian from the normal configuration of $^{32}$Al and determined their modification by the $\chi^2$ fitting. Based on this analysis, we propose a new interaction, SDPF-MG04, which reproduces degeneracy of the $2^+$ and $4^+$ in $^{26}$F and the correct excited-state ordering in $^{32}$Al consistently, while maintaining the overall description of other nuclei in the model space.