Quantum Effects in Chemical Reactions under Polaritonic Vibrational Strong Coupling

TL;DR

This paper develops a quantum transition state theory to understand how vibrational strong coupling in optical cavities influences chemical reactions, explaining resonance, collective effects, and selectivity.

Contribution

It introduces a quantum framework for cavity-modified reactions, predicting how cavity frequency tuning affects reaction rates and pathways, advancing the understanding of VSC phenomena.

Findings

Resonance effect maximizes reaction modification at specific cavity frequencies.

Reaction rate scales linearly with molecular density under VSC.

Cavity-induced control can alter reaction selectivity and branching ratios.

Abstract

The electromagnetic field in an optical cavity can dramatically modify and even control chemical reactivity via vibrational strong coupling (VSC). Since the typical vibration and cavity frequencies are considerably higher than thermal energy, it is essential to adopt a quantum description of cavity-catalyzed adiabatic chemical reactions. Using quantum transition state theory (TST), we examine the coherent nature of adiabatic reactions and derive the cavity-induced changes in eigen frequencies, zero-point-energy, and quantum tunneling. The resulting quantum TST calculation allows us to explain and predict the resonance effect (i.e., maximal kinetic modification via tuning the cavity frequency), collective effect (i.e., linear scaling with the molecular density), and selectivity (i.e., cavity-induced control of the branching ratio). The TST calculation is further supported by perturbative analysis of polariton normal modes, which not only provides physical insights to cavity-catalyzed chemical reactions but also presents a general approach to treat other VSC phenomena.