Non empirical LCAO SCF MO investigations of electronic reorganizations accompanying core ionizations

Abstract

Calculations have been carried out on an extensive series of molecules for both the neutral species and core ionized states. Substituent effects on C1s, N1s, O1s, and F1s levels have been investigated and where available comparison has been drawn with experiment. Comparison with Koopmans' theorem has allowed a relatively detailed study of change in relaxation energies as a function of substituent effect on a given core level. Whilst for C1s levels the computed shifts in core binding energies are approximately linearly related to differences in relaxation energies for the N1s, O1s, and F1s levels, the relative electronegativity of the substituent can invert this correlation. The empirical correction of Koopmans' theorem for differences in relaxation energies at different sites has been investigated for large molecules. The results compare well with direct hole state calculations.