Looking at Eq. 192, the similarity between the vibration-phonon coupling (the second term) and the vibration-photon coupling (the third term) is apparent; for a linear permanent dipole µ gg (R) = µ 0 • R, both second and third terms take the form of a typical Caldeira-Leggett system-bath Hamiltonian. 379 Therefore, as much of the theories demonstrate, cavity modes act as additional solvent degrees of freedom providing fluctuations and dissipation to the reaction coordinate, resulting in the dynamical caging effect, or re-distributing vibrational energy, hence leading to modifications of the reaction rate constant.