Threshold photodetachment of ${\mathrm{H}}^{\mathrm{-}}$

The electron affinities of atomic hydrogen and deuterium have been determined by tunable-laser threshold-photodetachment spectroscopy: the electron affinities of H (F=0) and D (F=1/2) are 6082.99±0.15 and 6086.2±0.6 ${\mathrm{cm}}^{\mathrm{-}1}$, respectively. The value for H is a 20-fold improvement over previous experimental determinations.