the reaction rate constant will be enhanced or suppressed, typically up to 4-5 times compared to the rate constants outside the cavity. If we define |ν L ⟩ as the vibrational ground state of the reactant (left well), and |ν ′ L ⟩ as the vibrationally excited state of the reactant, then ω 0 = (E ′ -E)/h corresponds to the frequency of the |ν L ⟩ → |ν ′ L ⟩ transition. This universal experimental evidence strongly suggests that the optical measurements of the vibration and the cavity modification correspond to the same quantum transition |ν L ⟩ → |ν ′ L ⟩, such that both the optical spectra and the VSC rate constant modification are centered around ω 0 . Indeed, the optical transition is caused by -μ • E(t), where μ is the transition dipole operator, and E(t) is the classical laser field, whereas the molecule-cavity coupling is caused by μ(â † + â) ∝ μ • qc , where â † and â are cavity field operators and qc = h/2ω c (â † + â) is the photonic coordinate that is proportional to the displacement field intensity inside the cavity. The shape resonance of the VSC-modified rate constant has been shown in recent quantum dynamics simulations, with the effect indeed maximizes according to Eq. 1.