Analysis of the 3He(α,γ)7Be and 3H(α,γ)7Li astrophysical direct capture reactions in a modified potential-model approach

Astrophysical S factors and reaction rates of the direct radiative capture processes He3(α,γ)7Be and H3(α,γ)7Li, as well as the primordial abundance of the Li7 element, are estimated in the framework of a modified two-body potential model. It is shown that suitable modification of phase-equivalent α−3He potentials in the d waves can improve the description of the astrophysical S factor for the direct He3(α,γ)7Be radiative capture reaction at energies above 0.5 MeV. An estimated Li/H7 abundance ratio of (4.89±0.18)×10−10 is in very good agreement with the recent measurement of (5.0±0.3)×10−10 by the LUNA collaboration.