Ground and excited states of doubly open-shell nuclei from ab initio valence-space Hamiltonians

TL;DR

This paper uses ab initio methods with chiral interactions and in-medium similarity renormalization group techniques to accurately predict ground and excited states of doubly open-shell fluorine and neon isotopes, including deformation effects.

Contribution

It introduces a new targeted normal-ordering procedure within the in-medium similarity renormalization group framework to improve predictions for open-shell nuclei.

Findings

Reproduces experimental ground-state energies up to neutron number N=14.

Achieves good agreement with experimental spectroscopy for neutron-rich isotopes near N=14,16.

Provides an ab initio description of deformation in medium-mass nuclei like 20Ne and 24Mg.

Abstract

We present ab initio predictions for ground and excited states of doubly open-shell fluorine and neon isotopes based on chiral two- and three-nucleon interactions. We use the in-medium similarity renormalization group, in both flow-equation and Magnus formulations, to derive mass-dependent sd valence-space Hamiltonians. The experimental ground-state energies are reproduced through neutron number N=14, beyond which a new targeted normal-ordering procedure improves agreement with data and large-scale multi-reference calculations. For spectroscopy, we focus on neutron-rich 23-26F and 24-26Ne isotopes near N=14,16 magic numbers. In all cases we find an agreement with experiment competitive with established phenomenology. Moreover, yrast states are well described in 20Ne and 24Mg, providing an ab initio description of deformation in the medium-mass region.