Energy Transfer Rate Coefficients from Trajectory Calculations and Contributions of Supercollisions to Reactive Rate Coefficients

Abstract

Quasiclassical trajectory calculations on the CS2−CO system were performed. Analytical biexponential functions were fit to the trajectory results, and energy-dependent energy transfer transition probability functions and rate coefficients were derived. They, in turn, were used in solutions of master equations. Unimolecular rate coefficients for cyclobutane fission and cyclobutene isomerization in Ar bath gas at various temperatures were obtained. Supercollisions, collisions which transfer more than 5 times the average energy transferred in a down collision, were found to contribute to the high-energy tail of the biexponential transition probability function. To assess their contribution to the unimolecular rate coefficients, their values which were obtained from trajectory-based double-exponential transition probabilities are compared with those obtained from single-exponential weak-collision transition probabilities. For cyclobutane fission an ∼5-fold increase in the value of the rate coefficient is foun...