where k 1 is the rate constant for the vibrational excitation of the reactant (left well), k 2 is the rate constant of transition between the vibrational excited states of the left and right well, and k 3 corresponding to the vibrational relaxation process in the right well. Through exact quantum dynamics simulation, we observed that k 1 ≪ k 2 , k 3 , making |ν L ⟩ → |ν ′ L ⟩ rate-limiting. Further, we found that the role of the cavity mode qc is to promote the vibrational excitation and enhance k 1 . Using the steady-state approximation and Fermi's Golden Rule (FGR) rate theory, the overall rate constant is approximated as k ≈ k 1 = k 0 +k VSC , where k 0 is the outside cavity rate constant (which means in the absence of cavity modes throughout this paper), and k VSC is the cavityenhanced rate constant. Including the cavity mode and its loss environment in an effective spectral density , k VSC can be evaluated using FGR, expressed as