Ab initio mapping of the boundary of the $N=20$ island of inversion

Abstract

Starting from a chiral two- plus three-nucleon interaction, we perform a systematic study of the low-lying states of neutron-rich nuclei around $N=20$ using the in-medium generator coordinate method (IM-GCM), which combines the multi-reference in-medium similarity renormalization group (MR-IMSRG) with the quantum-number projected generator coordinate method (PGCM) defined in a full single-particle space. The main features of the energy spectra and electromagnetic properties of low-lying states in both even-even and odd-mass nuclei of this mass region are reasonably reproduced. The boundary of the $N=20$ island of inversion (IOI) is investigated, and the results indicate that ${}^{30}$Ne, ${}^{29,31,33}$Na, ${}^{31-34}$Mg, and ${}^{35}$Al lie within the IOI, whereas ${}^{29}$F, ${}^{29}$Ne, ${}^{30}$Mg, ${}^{31,33}$Al, ${}^{34,35}$Si, and ${}^{35}$P fall outside it.

17 pages with 15 figures and 1 table