Collective excitations in deformed sd-shell nuclei from realistic interactions

TL;DR

This paper demonstrates that realistic nucleon-nucleon interactions, when properly transformed, can accurately describe collective excitations in deformed sd-shell nuclei, matching or surpassing phenomenological models.

Contribution

It extends the application of realistic interactions to deformed nuclei and compares their performance with phenomenological interactions for collective excitations.

Findings

Realistic interactions describe collective responses well.

Angular momentum projection significantly impacts results.

Good agreement with experimental data achieved.

Abstract

Background: Collective excitations of nuclei and their theoretical descriptions provide an insight into the structure of nuclei. Replacing traditional phenomenological interactions with unitarily transformed realistic nucleon-nucleon interactions increases the predictive power of the theoretical calculations for exotic or deformed nuclei. Purpose: Extend the application of realistic interactions to deformed nuclei and compare the performance of different interactions, including phenomenological interactions, for collective excitations in the sd-shell. Method: Ground-state energies and charge radii of 20-Ne, 28-Si and 32-S are calculated with the Hartree-Fock method. Transition strengths and transition densities are obtained in the Random Phase Approximation with explicit angular-momentum projection. Results: Strength distributions for monopole, dipole and quadrupole excitations are analyzed and compared to experimental data. Transition densities give insight into the structure of collective excitations in deformed nuclei. Conclusions: Unitarily transformed realistic interactions are able to describe the collective response in deformed sd-shell nuclei in good agreement with experimental data and as good or better than purely phenomenological interactions. Explicit angular momentum projection can have a significant impact on the response.