Quadrupole collectivity beyond N=28: Intermediate-energy Coulomb excitation of 47,48Ar

TL;DR

This study investigates quadrupole collectivity in neutron-rich argon isotopes using Coulomb excitation, revealing challenges for shell-model descriptions near N=28 and providing new experimental data in this critical shell evolution region.

Contribution

First experimental measurement of quadrupole collectivity in {47,48}Ar using intermediate-energy Coulomb excitation, testing shell-model predictions in a key shell evolution region.

Findings

Measured B(E2) transition strengths for {47,48}Ar.

Comparison shows shell-model struggles to accurately predict properties near N=28.

Highlights the need for improved theoretical models in this neutron-rich region.

Abstract

We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei \nuc{47,48}{Ar} using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly-magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced $B(E2)$ transition strengths are confronted with large-scale shell-model calculations in the $sdpf$ shell using the state-of-the-art SDPF-U and EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.