R-matrix theory of electron-molecule scattering

Abstract

A general R-matrix theory of low-energy electron scattering by diatomic molecules is developed. The theory is based on the frame-transformation approach of Chang and Fano (1972) in which different representations are used for different ranges of the electron-molecule distance coordinate. Particular emphasis is given to short distances where exchange and correlation effects between the electron and the molecule are strong, and it is shown in detail how the R matrix on the surface of this region can be expressed in terms of a multi-centre configuration-interaction wavefunction. Finally, a description is given of the numerical procedures which are used in the calculation of electron collision cross sections for an arbitrary diatomic molecule.