Testing microscopically derived descriptions of nuclear collectivity: Coulomb excitation of 22Mg

TL;DR

This paper measures the E2 transition strength in 22Mg and 22Ne via Coulomb excitation, providing data to test microscopic nuclear theories that aim to describe collectivity without effective charges.

Contribution

It offers precise experimental E2 data for 22Mg and 22Ne to compare with ab initio nuclear theory calculations, highlighting discrepancies and components of missing strength.

Findings

No-core symplectic shell-model agrees with measured B(E2) values.

In-medium SRG calculations underpredict absolute E2 strength.

Missing strength has both isoscalar and isovector components.

Abstract

Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be dealt with in an {\it ab initio} framework without the use of effective charges; for example with the proper evolution of operators, or alternatively, through the use of an appropriate and manageable subset of particle-hole excitations. We present a precise determination of $E2$ strength in $^{22}$Mg and its mirror $^{22}$Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new $B(E2)$ values while in-medium similarity-renormalization-group calculations consistently underpredict the absolute strength, with the missing strength found to have both isoscalar and isovector components.