The autodetachment of 1s2s2p ${}_{}{}^4{}_{}{}^{}$${\mathit{P}}^{\mathit{o}}$ in ${\mathrm{He}}^{\mathrm{-}}$ and ${\mathit{nsnp}}^2$ ${}_{}{}^4{}_{}{}^{}$${\mathit{P}}^{\mathit{e}}$ in ${\mathrm{Be}}^{\mathrm{-}}$ (n=2), ${\mathrm{Mg}}^{\mathrm{-}}$ (n=3), and ${\mathrm{Ca}}^{\mathrm{-}}$ (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 ${\mathrm{He}}^{\mathrm{-}}$ and ${\mathrm{Be}}^{\mathrm{-}}$ our results agree with earlier experimental and theoretical ones, and do predict a long-lived component. In ${\mathrm{Mg}}^{\mathrm{-}}$ and ${\mathrm{Ca}}^{\mathrm{-}}$, 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.

• Received 8 March 1991

DOI:https://doi.org/10.1103/PhysRevA.44.72