Nonequilibrium effects of cavity leakage and vibrational dissipation in thermally-activated polariton chemistry

TL;DR

This study uses kinetic simulations to explore how cavity leakage and vibrational dissipation influence thermally-activated reactions under vibrational strong coupling, revealing that dissipation accelerates thermalization and suppresses nonequilibrium effects, aligning with experimental findings.

Contribution

It demonstrates how cavity decay and vibrational dissipation affect reaction dynamics under vibrational strong coupling, providing insights beyond traditional transition-state theory.

Findings

Cavity decay accelerates internal thermalization, reducing nonequilibrium effects.

Dissipative processes can alter reactivity by influencing thermalization timescales.

Reactivity remains unchanged when the reaction is already at thermal equilibrium.

Abstract

In vibrational strong coupling (VSC), molecular vibrations strongly interact with the modes of an optical cavity to form hybrid light-matter states known as vibrational polaritons. Experiments show that the kinetics of thermally activated chemical reactions can be modified by VSC. Transition-state theory, which assumes that internal thermalization is fast compared to reactive transitions, has been unable to explain the observed findings. Here, we carry out kinetic simulations to understand how dissipative processes, namely those that VSC introduces to the chemical system, affect reactions where internal thermalization and reactive transitions occur on similar timescales. Using the Marcus-Levich-Jortner type of electron transfer as a model reaction, we show that such dissipation can change reactivity by accelerating internal thermalization, thereby suppressing nonequilibrium effects that occur in the reaction outside the cavity. This phenomenon is attributed mainly to cavity decay (i.e., photon leakage), but a supporting role is played by the relaxation between polaritons and dark states. When nonequilibrium effects are already suppressed in the bare reaction (the reactive species are essentially at internal thermal equilibrium throughout the reaction), we find that reactivity does not change significantly under VSC. Connections are made between our results and experimental observations.