Autodetachment of negative ions

The autodetachment of 1s2s2p ⁴{P}ᵒ$ in ${He}^{{{-}}}$ and ${nsnp}²$ $⁴Pᵉ in Be^- (n=2), Mg^- (n=3), and Ca^- (n=4) is calculated using an extension to continuum processes of the multiconfiguration Hartree-Fock method. The main interest is to investigate the processes giving rise to long-lived, metastable states in negative ions. In He^- and Be^- our results agree with earlier experimental and theoretical ones, and do predict a long-lived component. In Mg^- and Ca^-, however, we do not find any corresponding long-lived state. The processes behind the decay of these states are investigated, and a comparison of the different systems is made.