On the Suppression and Enhancement of Thermal Chemical Rates in a Cavity

TL;DR

This paper investigates how optical cavities can modify thermal chemical reaction rates, revealing conditions for enhancement and the role of energy redistribution channels, especially in low-friction regimes, through atomistic simulations of HONO isomerization.

Contribution

It provides an atomistic analysis of cavity effects on chemical rates, identifying conditions for rate enhancement and explaining sharp resonances via energy redistribution channels.

Findings

Cavity coupling can enhance reaction rates in low-friction regimes.

Sharp resonances are linked to cavity-enabled energy redistribution.

Rate enhancement persists until the Kramers turnover point.

Abstract

The observed modification of thermal chemical rates in Fabry-Perot cavities remains a poorly understood effect theoretically. Recent breakthroughs explain some of the observations through the Grote-Hynes theory, where the cavity introduces friction with the reaction coordinate, thus reducing the transmission coefficient and the rate. The regime of rate enhancement, the observed sharp resonances at varying cavity frequencies, and the survival of these effects in the collective regime remain mostly unexplained. In this paper, we consider the \emph{cis}-\emph{trans} isomerization of HONO atomistically using an \emph{ab-initio} potential energy surface. We evaluate the transmission coefficient using the reactive flux method and identify the conditions for rate acceleration. In the underdamped, low-friction regime of the reaction coordinate, the cavity coupling enhances the rate with increasing coupling strength until reaching the Kramers turnover point. Sharp resonances in this regime are related to cavity-enabled energy redistribution channels.