Collision Theory and Activated Complexes in Bimolecular Gas-Phase Reactions

The quasiequilibrium hypothesis for bimolecular reactions, which, as Marcus has shown, provides a bridge between the transition-state theory and the scattering theory of these reactions, was investigated from the standpoint of scattering theory. A modified formulation of R-matrix theory was employed. Assumptions necessary in order to unambiguously define a state of the activated complex and the transmission coefficient for this state in scattering-theory terms were given and partially justified. Approximations to the transmission coefficient expression thus formulated were considered, and relations between these approximations and the Marcus assumptions of adiabaticity, statistical adiabaticity, and separable reaction coordinate motion were noted.