Classical canonical transformation theory as a tool to describe multidimensional tunnelling in reactive scattering. Hopping method revisited and collinear H+H2 exchange reaction near the classical threshold

Abstract

Classical canonical perturbation theory is applied in the vicinity of the saddle point for a chemical reaction. This is done by applying successive canonical transformations in the scope of the GustavsonÈBirkho † approach. It is shown that the calculated approximate classical integrals of motion can be used to describe classically forbidden tunnelling processes. They are also organically embedded into a hopping method to incorporate tunnelling e †ects into classical trajectory simulations of chemical reactions. The applicability of the proposed scheme is demonstrated for the collinear exchange reaction using the double many-body H ] H 2 expansion potential energy surface.