Gamow shell model description of the radiative capture reaction 8Li(n, γ)9Li

Background: The Li-8(n, gamma)Li- 9 reaction plays a critical role in several reaction chains leading to the nucleo-synthesis of A > 12 nuclei. Due to unstable nature of Li-8 and the unavailability of neutron targets, direct measurements of this reaction are exceedingly difficult. Only upper limits of this cross section, provided by the indirect experiments, have been obtained so far. Purpose: In this work, we use the Gamow shell model (GSM) in the coupled-channel representation (GSM-CC) to study the properties of Li-9 and the radiative capture reaction Li-8(n, gamma ) Li-9. Method: GSM-CC is a theoretical framework allowing for the description of both nuclear structure and reaction cross sections. In GSM-CC calculations, a translationally invariant Hamiltonian is used with a finite-range two-body interaction tuned to reproduce the low-energy spectra of Li-8,Li-9. The reaction channels are built by coupling wave functions of the ground state 2(1)(+), the first-excited state 1(1)(+), and the first resonance state 3(1)(+) in Li-8 with the neutron wave function of the projectile in different partial waves. In the calculation of Li-8(n, gamma ) Li-9 cross section, all relevant E1, M1, and E2 transitions from the initial continuum states to the final bound states 3/2(1)(-), 1/2(1)(-) and the resonance 5/2(1)(-) of Li-9 are included. Results: The GSM-CC approach reproduces the experimental low-energy spectrum, neutron emission threshold, and spectroscopic factors in Li-9. The calculated reaction rate is consistent with the experimental upper limit of the reaction rate obtained in the indirect measurements at stellar energies. Conclusion: The GSM-CC calculations suggest that the Li-8(n, gamma) Li-9 reaction does not reduce significantly , heavy-element production via the main chain Li-7(n, gamma )Li-8(alpha, n)B-11(n, gamma)B-12 (beta(+))C-12. Major contribution to the calculated cross section is given by the direct E1 transition to the ground state of Li-8. The contribution of excited states to the reaction rate does not exceed approximate to 20% of the total reaction rate.

Automated summary

This study investigates the properties of Li-9 and the reaction cross section Li-8(n, gamma)Li-9 using the GSM-CC model. The results suggest that this reaction does not significantly impact heavy-element production and is primarily driven by direct E1 transition to the ground state of Li-8.