Electron Transfer in Strong Light-Matter Coupling: Does Increased Concentration Always Enhance Reaction Rates?

Strong light-matter coupling in an optical cavity leverages the collective interactions between molecules and confined electromagnetic fields, offering new avenues for controlling chemical reactivity and molecular properties. While enhanced Rabi splitting is a well-known spectroscopic signature observed with large numbers of molecules, its impact on electron transfer remains unclear. In this talk, we present recent results on non-adiabatic electron transfer processes in donor-acceptor pairs, influenced by collective excitations and local molecular dynamics. Our results demonstrate a non-monotonic dependence of the electron transfer rate on the number of molecules, driven by the interplay between molecular reorganization and polariton relaxation. Furthermore, we establish a relation between the thermal bath frequency and molecular concentration, providing predictive insights into the optimal conditions for maximizing cavity-controlled reactivity.