Quantum Control of Ultrafast Internal Conversion Using Nanoconfined Virtual Photons.

The rational control of nonradiative relaxation remains an unfulfilled goal of synthetic chemistry. In this study, we show how strongly coupling an ensemble of molecules to the virtual photons of an electromagnetic cavity provides a rational handle over ultrafast, nonradiative dynamics. Specifically, we control the concentration of zinc tetraphenyl porphyrin molecules within nanoscale Fabry-Perot cavity structures to show a variable collective vacuum Rabi splitting between cavity polaritons coincides with systematic changes in internal conversion rates. We find these changes deviate from the predictions of so-called gap laws. We also show that simple theories of structural changes caused by polariton formation cannot explain discrepancies between our results and established theoretical predictions. In light of these deficiencies, we explore other ways to explain the dependence of the internal conversion rate on polariton parameters. Our results demonstrate cavity polariton formation controls the photophysics of light harvesting and photocatalytic molecular moieties and the gap remaining in our fundamental understanding of mechanisms enabling this control.