Energy and lifetime of O2− from analytic continuation of isoelectronic bound states

We offer a method for determining the stability of dinegative ions for isoelectronic series exhibiting a bound singly charged anion. Nonlinear variational ground state energies obtained with bound, multiconfigurational wavefunctions are followed above the first ionization threshold as the nuclear charge (1/λ) is decreased. Resonance energies and widths for physical states are constructed by analytically continuing the energy around a singularity at a nonphysical λ=λ*. Results for the Ne isoelectronic series predict an O2− resonance state at 5.38 eV (width = 1.3 eV) above the O− + e− continuum theshold. The marked O2− instability suggests that estimates of the O− electron affinity, arising from thermochemical Born–Haber cycles, may require quantum corrections. We also discuss several chemical systems for which the method will be useful and which may lead to predictions of bound states existing in the continuum.