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

TL;DR

This study uses advanced nuclear many-body methods to map the boundary of the $N=20$ island of inversion, identifying which neutron-rich nuclei exhibit inverted shell structures.

Contribution

It provides a systematic ab initio analysis of the $N=20$ island of inversion boundary using the IM-GCM approach, combining MR-IMSRG and PGCM techniques.

Findings

Identifies nuclei within the $N=20$ island of inversion.

Accurately reproduces energy spectra and electromagnetic properties.

Maps 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.