Resonance theory of vibrational strong coupling enhanced polariton chemistry and the role of photonic mode lifetime

Recent experiments demonstrate polaritons under the vibrational strong coupling (VSC) regime can modify chemical reactivity. Here, we present a complete theory of VSC-modified rate constants when coupling a single molecule to an optical cavity, where the role of photonic mode lifetime is understood. The analytic expression exhibits a sharp resonance behavior, where the maximum rate constant is reached when the cavity frequency matches the vibration frequency. The theory explains why VSC rate constant modification closely resembles the optical spectra of the vibration outside the cavity. Further, we discussed the temperature dependence of the VSC-modified rate constants. The analytic theory agrees well with the numerically exact hierarchical equations of motion (HEOM) simulations for all explored regimes. Finally, we discussed the resonance condition at the normal incidence when considering in-plane momentum inside a Fabry-Pérot cavity. Polariton chemistry, namely the coupling of molecular vibrations to quantized radiation modes inside an optical microcavity, offers a promising strategy to modify chemical reactivities. Here, the authors provide a comprehensive theory of how vibrational strong coupling modifies chemical reaction rates in different cavity regimes.