The 3H(α,γ)7Li reaction below Ec.m. = 1 MeV

The 3H(α,γ) reaction, and its mirror 3He(α,γ) are responsible for 7Li production in the big bang. It has been demonstrated that the uncertainty in the 3H(α,γ) reaction rate significantly affects the calculated amount of 7Li, which is important for comparison to the observed 7Li abundance and constraining the baryon density allowed by the standard big-bang model. Using specially prepared thin Ti-3H targets and an 85% high-purity germanium detector, the authors have measured the γ rays produced by the 3H(α,γ) reaction for 50 < Ec.m. < 850 keV. They present the measured astrophysical S-factors, branching ratios for direct capture to the two final 7Li bound states, and angular distributions of the capture γ rays. The results are compared to previous experiments and nuclear model calculations