On the ordering of the ionization energies in N 2: A MC SCF study of near-degeneracy effects

Abstract

Single configuration SCF wavefunctions yield poor results for the order and relative energies of low-lying icnic states of N 2. A multi-configurational SCF (MC SCF) model which takes account of the near degeneracy of a small number of strongly and weakly occupied orbitals corrects the errors of the SCF approach. MC SCF results for N 2 predict the correct ordering and give reasonably accurate results for the three lowest ionization potentials.