Gamow shell model description of radiative capture reactions 6Li(p, γ)7Be and 6Li(n, γ)7Li

Abstract

Background. 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. Purpose. In this work we apply the Gamow shell model formulated in the coupled-channel representation to investigate the mirror radiative capture reactions 6Li(p, γ)7Be and 6Li(n, γ)7Li. Method. 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 6-7Li, 7Be. The reaction channels are built by coupling the wave functions of ground state and excited states ,31+,01+,21+ of 6Li with the projectile wave function in different partial waves. Results. We include all relevant E1, M1, and E2 transitions from the initial continuum states to the final bound states and of 7Li and 7Be. Our microscopic astrophysical factor for the 6Li(p, γ)7Be reaction follows the average trend of the experimental value as a function of the center of mass energy. For6(n,γ)Li, the calculated cross section agrees well with the data from the direct measurement of this reaction at stellar energies. Conclusion. We demonstrate that the s-wave radiative capture of proton (neutron) to the first excited state Jπ = 1+ of 7Be (7Li) is crucial and increases the total astrophysical S-factor by about 40%.