A simulation study of energy transfer in methyl isocyanide-inert gas collisions Original Research Article

The collisional energy transfer between inert gas atoms and highly excited methyl isocyanide (CH3NC) molecules has been studied by comparing the results of classical trajectory scattering calculations to ergodic-limit estimates obtained by Monte Carlo simulation. The dependence of the average energy transferred per collision on initial target (CH3NC) energy and medium (He, Ne, Ar, or Xe) temperature has been investigated. The energy transferred has been separated into rational and vibrational contributions to the total, with the not-unexpected result being that vibrational energy transfer is inefficient when compared to rotation. The implications of the near vibrational adiabaticity of the collisions have been addressed by extensions of the Ergodic Collision Theory. Additional investigations were performed to explore the sensitivity of the energy transfer to the strength of the interaction between reactant and medium particles, and to study the convergence of dynamical results and statistical predictions for increasing strengths of intermolecular interaction. A physically-grounded functional form for the energy transfer kernel P(E′|E) based on the statistical analysis is proposed, and is found to accurately reproduce the results of trajectory calculations.