Gamow shell model description of radiative capture reactions $^6$Li$(p,\gamma)$$^7$Be and $^6$Li$(n,\gamma)$$^7$Li

TL;DR

This paper uses the Gamow shell model in a coupled-channel approach to accurately calculate radiative capture reaction cross-sections for lithium isotopes, providing insights relevant to stellar lithium abundance and evolution.

Contribution

It applies the Gamow shell model with a coupled-channel formulation to compute radiative capture reactions, incorporating various electromagnetic transitions and adjusting interactions to experimental data.

Findings

The model reproduces spectra and separation energies of lithium isotopes.

Including s-wave capture significantly increases the astrophysical S-factor.

The approach improves understanding of lithium nucleosynthesis in stars.

Abstract

According to standard stellar evolution, lithium abundance is believed to be a useful indicator of the stellar age. However, many evolved stars like red giants show huge fluctuations around expected theoretical abundances that are not yet fully understood. The better knowledge of nuclear reactions that contribute to the creation and destruction of lithium can help to solve this puzzle. In this work we apply the Gamow shell model (GSM) formulated in the coupled-channel representation (GSM-CC) to investigate the mirror radiative capture reactions $^6$Li$(p,\gamma)$$^7$Be and $^6$Li$(n,\gamma)$$^7$Li. The cross-sections are calculated using a translationally invariant Hamiltonian with the finite-range interaction which is adjusted to reproduce spectra, binding energies and one-nucleon separation energies in $^{6-7}$Li, $^7$Be. All relevant $E1$, $M1$, and $E2$ transitions from the initial continuum states to the final bound states $J={3/2}_1^-$ and $J={1/2}^-$ of $^7$Li and $^7$Be are included. We demonstrate that the $s$-wave radiative capture of proton (neutron) to the first excited state $J^{\pi}=1/2_1^+$ of $^7$Be ($^7$Li) is crucial and increases the total astrophysical $S$-factor by about 40 \%.