Theory of Subexcitation Electron Scattering by Molecules. I. Formalism and the Compound Negative-Ion States

The problem of slow-electron scattering by molecules is treated formally with explicit consideration of the possible effects of the compound negative-ion states. The formulation is based on the treatments for nuclear reactions and scattering, in particular the unified treatment recently advanced by Feshbach. The transition matrix for both direct and resonance scattering, describing the excitation of the nuclear motion of the target molecule, is obtained. The influence of the compound negative-ion states on the equivalent scattering potential for resonance scattering is investigated in some detail.