The role of tritium reactions in the cosmological lithium problem

The is a significant discrepancy between the observed and theoretically predicted abundances of Li in the cosmos. There is some indication that tritium induced reactions can explain the reduced Li in the cosmos. In general, tritium does not play a significant role in nucleosynthesis considerations, and therefore, the associated nuclear reactions have not been evaluated in detail. Tritium reactions are not typically considered significant, but there are a few short-lived nucleosynthesis scenarios in which tritium formation and tritium-induced reactions are critical and should not be neglected. The first scenario is the onset of nucleosynthesis during the third to tenth minutes after the Big Bang, when primordial isotopes such as hydrogen ($^1$H), deuterium ($^2$H), tritium ($^3$H), $^3$He, $^4$He, and small amounts of $^6$Li, $^7$Li and $^7$Be are produced. A second important site for tritium-induced reactions is associated with the reassembling of isotopes after the electron capture-induced core collapse of massive stars, while a third site includes the core conditions of two merging neutron stars. In these astrophysical scenarios with extreme temperatures and densities, all elements in the core are dissociated into protons, neutrons, and alphas, prior to the rebounce and subsequent expansion by neutrino-driven winds. The expansion and associated cooling leads to the reassembly of heavier nuclei in statistical equilibrium. This reassembling process is handicapped by the need for three particle interactions such as the triple-$alpha$ and the $alpha-alpha-n$ processes, which are not in equilibrium, but could be by-passed by tritium induced reactions and tritium's capacity to store the neutrons for a time period before releasing them again in subsequent nuclear reaction processes. The time period is directly correlated with the associated reaction rates. We consider these processes and try to establish improved reaction rates on the basis of the available experimental data, taking into account all open channels. Our results are of interest for nuclear astrophysics as well as high-intensity laser-driven acceleration techniques, where new dynamical quantum calculations promise a considerable enhancement in fusion reactions due to laser-nucleus interactions at deep subbarrier energies.