Ground-state properties of light 4n self-conjugate nuclei in ab initio no-core Monte Carlo shell model calculations with nonlocal NN interactions

We report J(pi) = 0(+) ground-state energies and point-proton radii of He-4, Be-8, C-12, O-16, and Ne-20 nuclei calculated by the ab initio no-core Monte Carlo shell model with the JISP16 and Daejeon16 nonlocal NN interactions. Ground-state energies are obtained in the basis spaces up to seven oscillator shells (N-shell = 7) with several oscillator energies ((h) over bar omega) around the optimal oscillator energy for the convergence of ground-state energies. These energy eigenvalues are extrapolated to obtain estimates of converged ground-state energies in each basis space using energy variances of computed energy eigenvalues. We further extrapolate these energy-variance-extrapolated energies obtained in the finite basis spaces to infinite basis-space results with an empirical exponential form. This form features a dependence on the basis-space size but is independent of the value of (h) over bar omega used for the harmonic-oscillator basis functions. Point-proton radii for these states of atomic nuclei are also calculated following techniques employed for the energies. From these results, it is found that the Daejeon16 NN interaction provides good agreement with experimental data up to approximately O-16, while the JISP16 NN interaction provides good agreement with experimental data up to approximately C-12. Beyond these nuclei, the interactions produce overbinding accompanied by radii that are too small. These findings suggest and encourage further revisions of nonlocal NN interactions towards the investigation of nuclear structure in heavier-mass regions.

Automated summary

In this study, J(pi) = 0(+) ground-state energies and point-proton radii of He-4, Be-8, C-12, O-16, and Ne-20 nuclei were calculated using the ab initio no-core Monte Carlo shell model with the JISP16 and Daejeon16 nonlocal NN interactions. The results show good agreement with experimental data up to approximately O-16 for Daejeon16, and up to approximately C-12 for JISP16, but beyond these nuclei, overbinding and overly small radii were observed. Further revisions of nonlocal NN interactions are suggested for investigations of nuclear structure in heavier-mass regions.