Molecular polaritons are collective excitation modes between delocalized exciton states across a macroscopic number of molecules and one or a few optical modes in a microcavity. The chemical processes featured by these modes have been subject of much recent investigation; however, many puzzles remain. In particular, the many dark modes that coexist with the polariton modes render chemical modification entropically unlikely in the absence of intense optical pumping. <br/><br/>Here I will present two recent results from my research group. The first one is that the many dark modes may not seen as trivial as they were previously considered; they are in fact delocalized across 2-3 molecules on average, a property that may lead to a faster thermalization en route to stabilization of products or intermediates. Thus, thermally-activated reactions in cavities supporting vibrational polaritons may feature different reaction rates compared to their bare molecular counterparts. However, these changes in chemical reaction rates are only possible if so-called dynamical effects are relevant, i.e., if vibrational relaxation processes compete with barrier crossing events. The second result is that to bypass the entropic fate of the many-dark states, one can optically pump the system to condensation threshold. The polariton condensate then becomes a very unusual bank from where molecules can draw energy to cross energy barriers.<br/><br/>Our results showcase the very interesting collective coherent phenomena that polaritons entail in connection with chemical reactivity.

Polariton chemistry: from thermally-activated to condensate-driven reactions

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.