Rotational transition states: relative equilibrium points in inelastic molecularcollisions

Abstract

Transition states (TSs) are a key ingredient in the understanding of many chemicalreactions. We present here a generalization of TS theory towards rotational excitationin molecular collisions, in a multi-dimensional classical Hamiltonian framework.The treatment is based on relative equilibrium, where the two colliding moleculesbehave as a single rotating solid object. We illustrate the theory with the help of asimple, yet meaningful, model potential for collisions between H2O andH2,which is of great importance in the astrophysical context. We show that it is theoccurrence of a rotational TS that opens up the possibility of significant angularmomentum transfer.