Configuration interaction calculations of the satellite peaks associated with C l s ionization of carbon monoxide

Abstract
Large scale configuration interaction calculations of the first five 2Σ+ carbon 1s core hole states of CO are described. Configuration selection, by means of perturbation theory, from ≳30 000 bonded functions yields final transition energies in good agreement with experiment. The inadequacy of a CI expansion including only singly excited configurations from the RHF reference configuration, is shown. A small CI expansion, using selected configurations, yields calculated intensities sufficiently accurate to allow an assignment of the experimental spectrum which is not possible from the calculated transition energies alone.