Group theoretical selection rules for electron-impact spectroscopy

Simple group theoretical principles are applied to the consideration of electron scattering off atoms and diatomic and polyatomic molecules. For all scattering angles Sg ↔ Su is forbidden for atoms. Fer axial scattering (0° or 180° scattering angle), Σ+ ⇹ Σ- for linear polyatomic molecules and Sg ⇹ Pg ⇹ Dg, etc., for atoms. This approach is also used to estimate relative strengths of electron-impact-induced transitions of diatomic and polyatomic molecules.