The orbital relaxation energy for single and double ionizations from valence shells of CH4, NH3, H2O and HF

The orbital relaxation energy is defined for single and double ionizations of valence electrons, and is calculated for CH₄, NH₃, H₂O and HF molecules with the ab initio SCF method. It is shown that the orbital relaxation energy for the ionization from a bonding orbital is about half of that for a non-bonding orbital, and the orbital relaxation energy for the double ionization is about double of that for the single ionization. This result gives a theoretical foundation for the empirical method of interpret Auger electron spectra by using experimental single ionization potentials.