In this model described by Eq. 192, the coupling between qc and R creates a hybridization between the molecular vibrational states and photonic states, forming vibrational polariton states separated with a Rabi-splitting (Fig. ). A simple expression for the Rabi-splitting can be obtained by considering the lightmatter interaction term in ĤPF (Eq. 192) at the equilibrium position of the reactant, R 0 . At R 0 , we may approximate the permanent dipole as linear function of R, µ gg (R) ≈ µ 0 + µ ′ 0 R, where µ(0) ≡ µ(R 0 ) is the permanent dipole at the reactant well and