These results show that the significant cavity enhancement is enabled by collective coupling to the cavity and depends sensitively on the collective Rabi splitting Ω R . The collective PMET rate constant cares about Ω R ∼ 2 √ Ng c , and thus is collective. Despite individual molecules being weakly coupled to the cavity mode with strength g c , as long as there are a large enough number of molecules N collectively coupled to the cavity, there will be a significant modification of the rate constant. This mechanism relies on the non-local light-matter interactions and local chemical couplings (between donor to acceptor through V DA ). This rate dependence on the collective Rabi splitting in this work could offer insight into the apparent Rabi splitting dependence of existing polariton photochemistry experiments such as the rate enhancement observed in Ref. 12. Future work includes analyzing the effects of multiple k-dispersed cavity modes on the PMET process as well as investigating both the electron-photon population dynamics and nuclear wavepacket dynamics of different photochemical model systems in the collective coupling regime.