RADICAL-RADICAL REACTIONS

Radical-radical reactions generally proceed on potential energy surfaces that have no maximum. Collisional deactivation leads to a stable molecular product; alternatively, radical or molecular products can be formed via dissociation channels additional to those regenerating the reactants. Models of the transition states must take into account the loose internal motion of the fragments, and a variational approach is necessary. The competition between dissociation and collisional stabilization may be modeled using a master equation (ME). The types of behavior encountered in radical-radical reactions and their analysis using the ME are illustrated by reference to the reactions CH3 + H, CH3 + CH3, and CH3 + OH.