VARIATIONAL PREDICTIONS OF TRANSITION ENERGIES AND ELECTRON-AFFINITIES - HE AND LI GROUND-STATES AND LI, BE, AND MG CORE-EXCITED STATES

Variational procedures for predicting energy differences of many-electron systems are investigated. Several different calculations for few-electron systems are considered that illustrate the problems encountered when a many-electron system is modeled as a core plus outer electrons. It is shown that sequences of increasingly more accurate calculations for outer correlation may converge yielding wrong transition energies. At the same time, accurate core-polarization calculations overestimate the binding energy, requiring a core-valence correction. For the high-spin, core-excited states of Li, it was found that outer correlation only predicted electron affinities as accurately as full-correlation studies. This observation suggested a prediction of the core-excited 4P-4S transition in Be-, based on observed 3P0-3P transition energies of the neutral species, predicted electron affinities including only outer correlation, and a core-valence correction, that is shown to be in good agreement with experiment. A similar calculation for Mg- predicts a wavelength of 2895.1 for this transition. © 1990 The American Physical Society.