Fig. illustrates how the light-matter coupling modifies chemical reactivities. As one increases Ω R (by increasing the light-matter coupling strength A 0 ), the rate constant decreases in a non-linear fashion which closely resembles the experimental trend in Fig. . For the PF Hamiltonian description that explicitly includes the DSE term, there is no change in k TST because there is no change of potential energy barrier. The only change in the rate comes from κ. The modification of κ (formally κ contributed to the change in entropy 374 ) will lead to the effective change of the free energy barrier height. To this end, we use the Eyring Rate equation to convert the change of rate from κ into an effective ∆(∆G ‡ ). The 4 times decrease in κ (blue curve in Fig. ) results in ∼ 4 KJ/mol change in "effective" ∆(∆G ‡ ) (red curve in Fig. ) at ∼ 700 cm -1 of Ω R . This theory indicates that such a non-linear increase of the "effective" ∆(∆G ‡ ) as increasing Ω R is in fact due to the change of κ.