Direct-Capture Model for the He3(α, γ)Be7 and T(α, γ)Li7 Reactions

Abstract

Using the He3+He4 scattering phase shifts, the cross section for the He3(α, γ)Be7 reaction is calculated on the basis of a He3+He4 model for the ground state and first excited state of Be7. Capture of particles from the S, P, D, and F partial waves by means of E1, M1, and E2 transitions is considered. The results are in excellent agreement with the experimental data presented in the preceding paper and indicate that the reaction proceeds chiefly by means of E1 capture from the S and D waves. It is a surprising consequence that the D wave contributes an appreciable fraction of the total capture cross section for alpha-particle energies as low as 1 MeV. Using the same values for the reduced widths of the final states that were determined for the He3(α, γ)Be7 reaction, similar calculations have also yielded excellent agreement with the experimental data for both the branching ratio and the total cross section of the mirror reaction T(α, γ)Li7.