Autodetachment of the nsnp2 4P1/2 states in negative ions

The purpose of this work is to compute the autodetachment rates of the nsnp2 P-4(1/2) levels for Be-(2s2p2), Mg-(3s3p2) and Ca-(4s4p2) . Fano's configuration interaction model is implemented to compute the interaction between the discrete and continuum spaces of the wavefunction, which are determined using the multiconfiguration Hartree-Fock technique. Analysing the decay mechanism of the P-4(1/2) components, we find large cancellation effects in the transition matrix for the interaction between the discrete perturbers and the ns2ksS-2(1/2) continuum channels, which makes the calculations very sensitive to computational details. We predict relatively long-lived metastable states with lifetimes in the range 10(-5)-10(-7) s, which, however, only for Be- remain in a qualitative agreement with the experiment. We also investigate the stability of the present approach in the light of the correlation in the discrete perturber and find a strong interplay between the representation of the ns2ks S-2(1/2) Continuum and the ns2n's S-2(1/2) Rydberg series.