Probing the polaritonic potential energy surface via Raman spectroscopy

Controlling chemical reactions using light has been a long-standing dream for chemists. Recently it has been shown that the rates of chemical reactions can be changed using light-matter hybrid particles. These light-matter hybrid particles, known as polaritons, form when there is a strong coupling between light and molecular excitation inside an optical cavity. These states have entirely new optical properties and have been used to show a wide range of phenomena such as exciton-polariton condensate, enhanced charge and long-range energy transport. However, the mechanism which is responsible for the changes brought upon by polariton formation in the reaction dynamics remains unclear. In order to understand the complete mechanism, which includes structure-function relationship, we must understand the changes in molecular structure in polariton potential energy surface. To study the effects of strong light-matter coupling in the excited state dynamics of photochemical reactions we have used advanced Raman techniques on pentacene exciton-polariton cavities. We have observed that the molecular structure changes upon polariton formation and the amount of change in the molecular structure can be tuned by various degrees of freedom provided by the cavity. Overall, our probe of polaritonic potential energy surfaces will enable us to tune the molecular structure in the polaritonic states which will help us in making efficient devices and control chemical reactions.