Regularity in chaotic reaction paths II: Ar6. Energy dependence and visualization of the reaction bottleneck

Abstract

Reaction trajectories reveal regular behavior in the reactive degree of freedom and unit transmission coefficients as the system crosses the saddle region separating reactants and products. The regularity persists up to moderately high energies, even when all other degrees of freedom are chaotic. This behavior is apparent in a representation obtained by transformation with Lie canonical perturbation theory. The dividing surface in this representation is analogous to the conventional dividing surface in the sense that it is the point set for which the reaction coordinate has the constant value it has at the saddle-point singularity. However the nonlinear, full phase-space character of the transformation makes the new crossing surface a complicated, abstract object whose interpretation and visualization, the objective of this paper, can be realized by cataloging the recrossings as they disappear in successively higher orders of perturbation, and by projection into spaces of only a few dimensions. The result is a conceptual interpretation of how regular behavior persists in a reactive degree of freedom.