We examine the possibility that big-bang nucleosynthesis (BBN) may produce nontrivial amounts of ${}^6\mathrm{Li}$. If a primordial component of this isotope could be observed, it would provide a new fundamental test of big-bang cosmology, as well as new constraints on the baryon density of the universe. At present, however, theoretical predictions of the primordial ${}^6\mathrm{Li}$ abundance are extremely uncertain due to difficulties in both theoretical estimates and experimental determinations of the ${}^2\mathrm{H}(\alpha ,\gamma {)}^6\mathrm{Li}$ radiative capture reaction cross section. We also argue that present observational capabilities do not yet allow the detection of primeval ${}^6$Li in very metal-poor stars of the galactic halo. However, if the critical cross section is very high in its plausible range and the baryon density is relatively low, then improvements in ${}^6\mathrm{Li}$ detection capabilities may allow the establishment of ${}^6\mathrm{Li}$ as another product of BBN. It is also noted that a primordial ${}^6\mathrm{Li}$ detection could help resolve current concerns about the extragalactic D/H determination.

• Received 16 December 1996

DOI:https://doi.org/10.1103/PhysRevC.56.1144