The structure and radiative lifetimes of negative ions homologous to N^-

Negative ions homologous to N^- are interesting systems, since there are several bound terms within the ground configuration. The forbidden transitions between them, often dominated by the magnetic dipole contributions, are affected by term mixing - a relativistic effect. When increasing the nuclear charge in the homologous sequence of negative ions, this effect increases. In this paper we use systematic multiconfiguration Dirac-Hartree-Fock calculations to study these effects and predict affinities, level splittings and transition rates between bound states of N^-, P^-, As^-, Sb^- and Bi^-. By monitoring the line strengths we are able to predict the deviation from the non-relativistic LS-coupled values for transitions between levels of the lowest ³P term. For Sb^- the ¹D term is also bound, and the prediction for the rates of its transition to the ³P-levels is a challenge for theory. For Bi^- less is known experimentally and we analyze its structure and the relativistic contributions to it.