  Bound state properties of the four-electron lithium ion Li$^{-}$ in its
ground $2^{2}S-$state and isotope-subsistuted ${}^{6}$Li$^{-}$ and
${}^{7}$Li$^{-}$ ions in their ground $2^1S-$state(s) are determined from the
results of accurate, variational computations. Another closely related problem
discussed in this study is accurate numerical evaluation of the half-life of
the beryllium-7 isotope. This problem is of paramount importance for modern
radiochemistry.

Atomic Physics