Branching ratios for He3(±)7Be and H3(±)7Li

Branching ratios for radiative alpha capture by tritium and He3 have been studied in a kinematical direct capture model for the purpose of obtaining an independent derivation of the H3(±)7Li branching ratio and possibly resolving an apparent discrepancy in the experimentally measured value. From the mirror symmetry between Li7 and Be7, and the observed branching ratio R(0)=0.38±0.04(1) for the He3(±)7Be reaction, the branching ratio for the H3()7Li reaction is constrained to be R(0)=0.47±0.07, which agrees best with the higher measured value. The implication of these results for big-bang nucleosynthesis in standard and nonstandard models is discussed.