Low-energy electron scattering by polar molecules

Abstract

A systematic theoretical study has been made of elastic, inelastic, total and momentum-transfer cross sections for thermal-energy electrons incident on dipolar target systems. Results are given for pure dipolar targets and for model molecular systems which include monopole, dipole and induced dipole terms in the electron-molecule interactions. The effect of critical dipole moments on low-energy momentum transfer cross sections is carefully examined and it is found that thermal-energy momentum-transfer cross sections for polar molecules are strongly affected by short-range screened coulomb and longer range induced dipole forces as well as the very long-range dipole term in the total scattering interactions. The use of a reasonable molecular field for a polar molecule essentially destroys any useful correlation between momentum-transfer cross sections and dipole moments for different polar molecules; thus there is no particular dipole magnitude which leads to a resonance effect in momentum-transfer cross sections for thermal-energy electrons on polar molecules. Relevant experimental data are discussed in the light of the present theoretical analysis.