Core-excited bound states of negative lithium

Accurate solutions of the four-electron Schrödinger nonrelativistic equation for nuclear charge $Z=3\mathrm{}$ reveal the existence of two core-excited bound states of ${\mathrm{Li}}^{-}$, which together with the ground state ${\mathrm{Li}}^{-}1s^{2}2s^2$ are found to be the only long-lived negative lithium ions. The metastable ${\mathrm{Li}}^{-}\left(1s2s2\mathrm{}{p}^2\right){}_{}{}^5{}_{}{}^{}P$ state is 504.5±2.0 meV below the (also metastable) $\mathrm{}\left(1s2s2p\right)\mathrm{}{}_{}{}^4{}_{}{}^{}P_{}^o{}_{}{}^{}$ state of Li. Another bound state ${\mathrm{Li}}^{-}\left(1s2\mathrm{}{p}^3\right){}_{}{}^5{}_{}{}^{}S_{}^o{}_{}{}^{}$, lies 291.0±2.0 meV below $\mathrm{Li}\left(1s2\mathrm{}{p}^2\right){}_{}{}^4{}_{}{}^{}P$ and it decays to the lower ${}_{}{}^5{}_{}{}^{}P$ state with $\tau =2.9\mathrm{}$ nsec, emitting uv photons of $\lambda =348.98\mathrm{}\pm 0.09$ nm. This is the first example of an electric dipole transition between bound states of atomic negative ions.