On the virtual-state effect in low-energy electron-CO₂ scattering

The threshold enhancement of the cross section for the excitation of the symmetric stretching mode of CO₂ by electron impact is described using a virtual-state model based on the projection-operator formalism of Feshbach. The analysis shows that the experimental data for the near-threshold (0, 0, 0) to (1, 0, 0) vibrational excitation cross section (Kochem et al., 1985) and the low-energy total electron-CO₂ scattering cross section (Ferch et al., 1981), as well as fixed-nuclei electron-CO₂ scattering calculations (Morrison), are compatible with the existence of a virtual-state pole of the fixed-nuclei scattering matrix close to the origin of the complex momentum plane.