Dynamical stereochemistry of activationless bimolecular reactions of ions and neutrals

An orientation-dependent centrifugal barrier model for describing the stereochemistry of reactions without activation energies is described. Applications to ion-polar molecule and atom-molecule reactions are discussed. The approach is similar in spirit to the line-of-centers model with an orientation-dependent activation barrier. It differs, however, from models that employ angle-averaged potentials; hence it recovers a steric factor (due to a limited cone of acceptance) and provides an explicit functional form for the orientation dependence of the reactivity within the cone.