Theory of electron-molecule scattering: Comments on the adiabatic-nuclei approximation

The adiabatic-nuclei theory of electron-molecule scattering is extended to account for electronic excitation of the target. The approximate expressions for the wave function and the scattering amplitude are derived from a formally exact expansion in terms of the fixed-nuclei, electronic-scattering solutions. The formalism treats molecular-bound and continuum states on an equal footing. We also propose a modified expression for the adiabatic-scattering amplitude which is expected to have an increased range of validity near excitation thresholds.