Charge radii of exotic neon and magnesium isotopes

TL;DR

This study calculates charge radii of exotic neon and magnesium isotopes using chiral effective field theory potentials and coupled-cluster methods, achieving good agreement with experimental data for many isotopes and providing insights into nuclear structure near the dripline.

Contribution

First ab initio calculations of charge radii for neon and magnesium isotopes using chiral potentials including delta isobars, with detailed analysis of subshell closures and isotope shifts.

Findings

Accurate charge radii for many isotopes with 2-3% uncertainty.

Reproduction of subshell closure at N=14 and decrease at N=8.

Underestimation of the large increase in charge radii at N=20 in magnesium.

Abstract

We compute the charge radii of even-mass neon and magnesium isotopes from neutron number N = 8 to the dripline. Our calculations are based on nucleon-nucleon and three-nucleon potentials from chiral effective field theory that include delta isobars. These potentials yield an accurate saturation point and symmetry energy of nuclear matter. We use the coupled-cluster method and start from an axially symmetric reference state. Binding energies and two-neutron separation energies largely agree with data and the dripline in neon is accurate. The computed charge radii have an estimated uncertainty of about 2-3% and are accurate for many isotopes where data exist. Finer details such as isotope shifts, however, are not accurately reproduced. Chiral potentials correctly yield the subshell closure at N = 14 and also a decrease in charge radii at N = 8 (observed in neon and predicted for magnesium). They yield a continued increase of charge radii as neutrons are added beyond N = 14 yet underestimate the large increase at N = 20 in magnesium.