Isospin symmetry breaking at high spins in the mirror pair 67Se and 67As

TL;DR

This study investigates the large mirror energy differences at high spins in 67Se and 67As, attributing them to isospin symmetry breaking effects involving the g9/2 orbit and proton pair excitations, using large-scale shell model calculations.

Contribution

It demonstrates the role of the g9/2 orbit and proton pair excitations in MED, providing new insights into isospin symmetry breaking at high spins.

Findings

Large MED due to proton pair excitations to g9/2 orbit.

Interference between electromagnetic spin-orbit and Coulomb monopole terms.

MED related to nuclear deformation.

Abstract

Recent experimental data have revealed large mirror energy differences (MED) between high-spin states in the mirror nuclei 67Se and 67As, the heaviest pair where MED have been determined so far. The MED are generally attributed to the isospin symmetry breaking caused by the Coulomb force and by the isospin nonconserving part of the nucleon-nucleon residual interaction. The different contributions of the various terms have been extensively studied in the fp shell. By employing large-scale shell model calculations, we show that the inclusion of the g9/2 orbit causes interference between the electromagnetic spin-orbit and the Coulomb monopole radial terms at high spin. The large MED are attributed to the aligned proton pair excitations from the p3/2 and f5/2 orbits to the g9/2 orbit. The relation of the MED to deformation is discussed.