Ab initio no-core solutions for $^6$Li

TL;DR

This paper employs ab initio methods to calculate properties of $^6$Li, including energies and radii, using advanced basis spaces and models, and compares results with experimental data.

Contribution

It introduces improved extrapolation methods and combines No-Core Full Configuration and Gamow Shell Model approaches with different interactions for $^6$Li.

Findings

Enhanced estimates of energies and radii up to Nmax=18

Significant convergence improvement using natural orbital basis

Consistent results across different interactions and models

Abstract

We solve for properties of $^6$Li in the ab initio No-Core Full Configuration approach and we separately solve for its ground state and $J^{\pi}=2_{2}^{+}$ resonance with the Gamow Shell Model in the Berggren basis. We employ both the JISP16 and chiral NNLO$_{opt}$ realistic nucleon-nucleon interactions and investigate the ground state energy, excitation energies, point proton root-mean-square radius and a suite of electroweak observables. We also extend and test methods to extrapolate the ground state energy, point proton root-mean-square radius, and electric quadrupole moment. We attain improved estimates of these observables in the No-Core Full Configuration approach by using basis spaces up through N$_{max}$=18 that enable more definitive comparisons with experiment. Using the Density Matrix Renormalization Group approach with the JISP16 interaction, we find that we can significantly improve the convergence of the Gamow Shell Model treatment of the $^6$Li ground state and $J^{\pi}=2_{2}^{+}$ resonance by adopting a natural orbital single-particle basis.