Quantum Control of Ultrafast Internal Conversion using Nano-Confined Virtual Photons

The rational control of non-radiative relaxation remains an unfulfilled goal for synthetic chemistry. In this study, we show strongly coupling an ensemble of molecules to the virtual photons of an electromagnetic cavity provides a rational handle over ultrafast, non-radiative dynamics. Specifically, we control the concentration of zinc tetraphenyl porphyrin molecules within nano-scale Fabry-Perot cavity structures to show a variable collective vacuum Rabi splitting between the polaritons coincides with changes in internal conversion rates. We find these changes obey a power law dependence on the collective vacuum Rabi splitting, but de- viate from the predictions of so-called gap laws. We also show simple theories of structural changes caused by polariton formation cannot explain discrepancies between our results and established theoretical predictions. Our results demonstrate a mechanism by which cavity polariton formation controls the fundamental photo-physics of light harvesting and photo- catalytic molecular moieties and the gap remaining in our fundamental understanding of these mechanisms.