The reactiond(α,γ)6Li at low energies and the primordial nucleosynthesis ofLi6

We have searched for the reaction d(α,γ${)}^6$Li at an α-d center-of-mass energy of 53 keV. An upper limit on the reaction S factor is 2.0×${10}^{\mathrm{-}7}$ MeV b at the 90% confidence level, corresponding to a limit on the synthesis of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ from a standard big bang of 0.9% of the present abundance for a total baryon-to-photon ratio 2.86<${\mathrm{\eta }}_{10}$<3.77. Equivalently, the ${}_{}{}^6{}_{}{}^{}\mathrm{-}_{}^7{}_{}{}^{}$Li isotopic abundance ratio immediately after a standard big bang is constrained to be less than 0.85%, considerably less than a recent measurement of this ratio in a metal-poor, Population II halo star. © 1996 The American Physical Society.