Abstract
Recent experiments demonstrate the control of chemical reactivities by coupling molecules inside an optical microcavity. In contrast, transition state theory predicts no change of the reaction barrier height during this process. Here, we present a theoretical explanation of the cavity modification of the ground state reactivity in the vibrational strong coupling (VSC) regime in polariton chemistry. Our theoretical results suggest that the VSC kinetics modification is originated from the non-Markovian dynamics of the cavity radiation mode that couples to the molecule, leading to the dynamical caging effect of the reaction coordinate and the suppression of reaction rate constant for a specific range of photon frequency close to the barrier frequency. We use a simple analytical non-Markovian rate theory to describe a single molecular system coupled to a cavity mode. We demonstrate the accuracy of the rate theory by performing direct numerical calculations of the transmission coefficients with the same model of the molecule-cavity hybrid system. Our simulations and analytical theory provide a plausible explanation of the photon frequency dependent modification of the chemical reactivities in the VSC polariton chemistry.
Highlights
Recent experiments demonstrate the control of chemical reactivities by coupling molecules inside an optical microcavity
We provide a theoretical explanation of the resonant vibrational strong coupling (VSC) polariton chemistry reactivities
We demonstrate that the resonant suppression of the reaction rate constant using the analytical GH rate theory as well as performing numerical calculations for a SM model molecular system coupled to a single-radiation mode inside an optical cavity
Summary
1⁄4 R and qc in panel (e) and (f), with a representative reactive trajectory on top (black solid curve). When the instantaneous friction is weak (jωCcj ( ωb), the GH theory becomes a model of non-equilibrium solvation, where the friction from the photonic coordinate qc does not severely impede the transitions[53] In this case, the transmission coefficient remains close to the case without the cavity (black curve in Fig. 2d), and the reactive trajectory crosses the barrier without much influence from qc. Our theory predicts that if VSC experiments can reach the ultrastrong coupling regime, the resonant frequency will be significantly shifted The origin of this resonant behavior in VSC chemical reaction rate constant (as indicated in Eq (7)) can be intuitively understood by examining representative trajectories (black solid curves) on the cavity BO potential energy surfaces presented in. The suppression of the chemical kinetics through the dynamical caging effect by the photon mode is highly sensitive to the photon frequency, proving a plausible mechanism for explaining the resonant behavior[21,23,24] of the reaction rate constant in VSC polariton chemistry
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