Dissociation of Molecules by Electron Impact

diagram of dissociation process

When a sufficiently energetic electron collides with a molecule, it can transfer some of its energy to the molecule to produce an electronically excited state. Very often the excited state will have a potential surface that is unbound along some coordinate, as shown here schematically for hexafluoroethane, and will dissociate to neutral fragments (radicals or atoms). Even if the excited state surface has a minimum, electron-impact excitation may lead to dissociation if the transition is to a point on the surface above the energy needed to dissociate.