On the Origin of Ground-State Vacuum-Field Catalysis: Equilibrium Consideration

Abstract: Recent experiments suggest that vibrational strong coupling (VSC) may significantly modify ground-state chemical reactions and their rates even without external pumping. The intrinsic mechanism of this "vacuum-field catalysis" remains largely unclear. Generally, modifications of thermal reactions in the ground electronic states can be caused by equilibrium or non-equilibrium effects. The former are associated with modifications of the reactant equilibrium distribution as expressed by the transition state theory of chemical reaction rates, while the latter stem from the dynamics of reaching and leaving transition configurations. Here, we examine the VSC effect in a cavity environment on chemical rates as calculated by transition state theory. Our approach is to examine the effect of coupling to cavity mode(s) on the potential of mean force (PMF) associated with the reaction coordinate. Within the context of classical nuclei and classical photons, we find that while the PMF can be affected by the cavity environment, this effect is negligible for the usual cavities used to examine VSC situations.