Summit of the N=40 Island of Inversion: precision mass measurements and ab initio calculations of neutron-rich chromium isotopes

TL;DR

This study combines high-precision mass measurements and ab initio calculations to explore the nuclear structure and deformation phenomena in neutron-rich chromium isotopes around N=40, providing insights into the island of inversion.

Contribution

It presents new precise mass measurements of chromium isotopes and applies ab initio models to analyze nuclear deformation at N=40, advancing understanding of this region.

Findings

Refined mass surface beyond N=40 for chromium isotopes.

Confirmed previous mass measurements with improved precision.

Provided a comprehensive picture of the N=40 island of inversion from calcium to nickel.

Abstract

Mass measurements continue to provide invaluable information for elucidating nuclear structure and scenarios of astrophysical interest. The transition region between the $Z = 20$ and $28$ proton shell closures is particularly interesting due to the onset and evolution of nuclear deformation as nuclei become more neutron rich. This provides a critical testing ground for emerging ab-initio nuclear structure models. Here, we present high-precision mass measurements of neutron-rich chromium isotopes using the sensitive electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our high-precision mass measurements of $^{59, 61-63}$Cr confirm previous results, and the improved precision in measurements of $^{64-65}$Cr refine the mass surface beyond N=40. With the ab initio in-medium similarity renormalization group, we examine the trends in collectivity in chromium isotopes and give a complete picture of the N=40 island of inversion from calcium to nickel.