Suppression and Enhancement of Thermal Chemical Rates in a Cavity

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 Letter, we consider the cis− trans isomerization of HONO atomistically using an 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.

Chemical reactions in imperfect cavities: enhancement, suppression, and resonance

“…After completing this work, we noticed that two similar results were reported in the literature. [35,36] Our work is in agreement with these findings and differentiates itself from those works as we investigated the effect of imperfect cavities, both numerically and analytically, on chemical reaction rates while the other reports focused on perfect cavities.…”

Resonant Cavity Modification of Ground-State Chemical Kinetics

“…When nuclear quantum effects are negligible, QTST provides the same result as the GH theory. Further, both the GH theory and QTST predict only a mild suppression of chemical kinetics and a broad rate profile , as a function of photon frequency, in contrast to the much larger and sharper rate profile typically observed in experiments. ,, On the other hand, computational studies , at the single-molecule level revealed the enhancement of the chemical kinetics, especially when the molecule–bath coupling is weak…”

“…Further, both the GH theory and QTST predict only a mild suppression of chemical kinetics and a broad rate profile 12,17 as a function of photon frequency, in contrast to the much larger and sharper rate profile typically observed in experiments. 1,5,8 On the other hand, computational studies 20,25 at the single-molecule level revealed the enhancement of the chemical kinetics, 25 especially when the molecule−bath coupling is weak. 28 Note that all such reaction theories are either classical or semiclassical in nature and do not address collective effects in a direct manner.…”

“…Despite recent theoretical progress, − the fundamental theoretical understanding of cavity-modified ground-state chemical reactivity remains inadequate. In short, the primary theoretical challenges regarding vibrational polaritonic chemistry include (i) explaining the resonance effect, namely the observation that chemical kinetics is strongly modified when the photon frequency is close to some vibrational frequency of the reactant molecule, and (ii) explaining collective effects, namely the observation that cavity-modified chemical reactivity depends on the number of molecules coupled to the radiation mode.…”

Polaritonic Chemistry from First Principles via Embedding Radiation Reaction

“…Furthermore, it illustrates clearly that the cavity influence on chemical reactivity can persist even at a large N ensemble and that the catalyzing and inhibiting effect could be present for the same chemical reaction. Recent work − , showed promising progress, and yet much remains to be investigated. A conclusive understanding will likely demand a collaborative effort involving experimental work, ab initio theory, and simplified models.…”