COLLISION-INDUCED ISOMERIZATION OF A SEMIRIGID BENDER HYDROGEN-CYANIDE

The isomerization of a hydrogen cyanide molecule from a localized HCN state to a localized HNC state is formulated as a bimolecular scattering process. The scattering partner is Ar, and the intermolecular interaction potential is written as a pairwise summation of Lennard-Jones potentials. The parameters of this potential are optimized to yield the correct Ar-hydrogen cyanide van der Waals structure. The intramolecular isomerization potential is based on an approximate reaction path through a three-dimensional ab initio potential, and HCN/HNC is treated as a semirigid bender. Eighty molecular eigenstates are calculated, and used as a coupled-channel basis in a scattering calculation in which the hydrogen cyanide rotation is treated in the infinite order sudden approximation. Transition probabilities and cumulative reaction probabilities to HNC states from initial HCN states are focused on; however, some results to final delocalized states are also presented. The bimolecular isomerization rate constant is presented over a wide temperature range. The energy transfer between Ar and initial HCN states is also briefly examined, as a function of the initial relative translational energy. © 1994 American Institute of Physics.