Kinematic model for four-center, AB+CD, reactions

Molecular dynamics simulations showing that high-barrier, four-center, reactions occur quite readily at elevated collision energies are presented. At such energies, the reaction is found to be super direct and the motion to, and down from, the barrier, is sudden-like. A simple kinematic model is shown to provide a remarkably accurate description of many aspects of the dynamics and, in particular, of the energy requirements and energy disposal in these reactions. The model emphasizes that over and above the energy necessary to overcome the high barrier to reaction, there is a strong kinematic constraint on the formation of products. Detailed results are reported for the N₂+O₂ reaction.