Abstract. Transition states (TSs) are a key ingredient in the understanding of many chemical reactions. We present here a generalization of TS theory towards rotational excitation in molecular collisions, in a multi-dimensional classical Hamiltonian framework. The treatment is based on relative equilibrium, where the two colliding molecules behave as a single rotating solid object. We illustrate the theory with the help of a simple, yet meaningful, model potential for collisions between H₂O and H₂, which is of great importance in the astrophysical context. We show that it is the occurrence of a rotational TS that opens up the possibility of significant angular momentum transfer.

Print publication: Issue 7 (14 April 2003)
Received 8 November 2002, in final form 13 February 2003
Published 14 March 2003