Resolving a discrepancy between experimental and theoretical lifetimes in atomic negative ions

A recent measurement of the lifetime of the excited 3p(5) P-2(1/2) state in the S- negative ion, which is dominated by a forbidden magnetic dipole transition to the P-2(3/2) ground state, reveals a discrepancy with earlier theoretical predictions. To investigate this we have performed systematic and large-scale multiconfiguration Dirac-Hartree-Fock calculations for this system. After including a careful treatment of correlation and relativistic effects, we predict a well-converged value for this lifetime, with an uncertainty considerably less than 1%, thereby removing the apparent conflict between theory and experiment. We also show that this result corresponds to the non-relativistic limit in the LS coupling approximation for the magnetic dipole transition within this P-2 term. In addition we demonstrate the usefulness of the latter approach for P-2 transitions in O-, Se- and Te-, as well as for analogous M1 transitions within D-2 terms in Ni- and Pt- ions.