The Quantum Normal Form Approach to Reactive Scattering: The Cumulative Reaction Probability for Collinear Exchange Reactions

TL;DR

This paper evaluates the quantum normal form method for calculating reaction probabilities in collinear exchange reactions, showing it works well for heavy atoms but poorly for light atoms due to tunnelling effects.

Contribution

It demonstrates the effectiveness and limitations of the quantum normal form approach in reactive scattering, highlighting its computational advantages and failure in light atom systems.

Findings

Accurately predicts reaction probabilities for heavy atom systems

Performs poorly for light atom systems due to tunnelling effects

Shows computational benefits over full reactive scattering methods

Abstract

The quantum normal form approach to quantum transition state theory is used to compute the cumulative reaction probability for collinear exchange reactions. It is shown that for heavy atom systems like the nitrogen exchange reaction the quantum normal form approach gives excellent results and has major computational benefits over full reactive scattering approaches. For light atom systems like the hydrogen exchange reaction however the quantum normal approach is shown to give only poor results. This failure is attributed to the importance of tunnelling trajectories in light atom reactions that are not captured by the quantum normal form as indicated by the only very slow convergence of the quantum normal form for such systems.