Sixteenth Spiers Memorial Lecture. Molecular ionization and molecular theory

Abstract

Methods of calculating the various electronic energy states of a molecular ion are discussed. If the same molecular orbitals are used as in the ground state of the molecule then further configuration interaction is required to obtain good wavefunctions. These wavefunctions give rise to corrections to the Koopmans' theorem values of the ionization potentials; the form of these corrections is considered both for valence shell and inner shell ionization. The role of semi-empirical and ab initio calculations of molecular wavefunctions in relation to experiment is discussed briefly and illustrated by reference to ionization potentials. Finally, the limitations of a discussion of the processes of ionization, reorganization and dissociation purely in terms of transitions between stationary states is pointed out and a simple model is presented which allows some more general concepts to be introduced.