On the theory of the state distribution of the reaction products and rates of unimolecular dissociations

Abstract

A recent variational implementation of RRKM theory, plus an additional dynamical assumption, is used to calculate the distribution of quantum states of reaction products of unimolecular dissociations. It is assumed that the “conserved” modes of the molecule are vibrationally adiabatic after passage through the transition state region, but that the “transitional modes” are non-adiabatic until the “loose transition state” region is reached. The rate constants k EJ themselves are those of RRKM theory, but, for energies below those needed to yield vibrationally excited products, the phase space theory expression (PST) is obtained for the distribution of rotational states of the products. The product state distribution differs from that of PST when the energy is sufficient to permit product vibrational excitation. The unimolecular reactions considered are those for which there is no potential energy barrier for the reverse reaction (recombination).