CAREER: Gas-Phase Molecular Polaritons: A New Platform for Chemistry under Strong Light-Matter Coupling

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Marissa Weichman of Princeton University is studying how gas-phase chemical processes proceed under strong interactions with light. When molecules are enclosed within an optical cavity, that is, in a device built from reflective mirrors that create a strong confined light field, new states called polaritons can form. These systems exhibit some of the unusual wave-like properties of light and also appear to demonstrate reactivity and photochemistry distinct from ordinary molecules. The principles governing the chemistry of polaritonic molecules are not currently well understood. The Weichman Lab is studying the low-temperature chemistry of isolated, gas-phase molecules under strong cavity coupling to elucidate how the simplest molecular polaritons behave. These discoveries have the potential to inform practical applications for polaritonic technologies in chemistry, materials science, and quantum information science. Professor Weichman is also reforming undergraduate quantum chemistry coursework at Princeton with the goal of broadening participation in the quantum science research community and workforce. The Weichman Lab will focus on pristine gas-phase measurements wherein polariton reaction dynamics can be studied with quantum-state-specificity and without the complications of solvation. While molecular polaritons are now well established in liquids and in solid-state systems, attaining sufficiently strong light-matter interactions for gas-phase molecules has remained a challenge. The Weichman Lab accesses the regime of gas-phase strong coupling at cryogenic temperatures where molecular partition functions are small and inhomogeneous linewidths are narrow. A cryogenic buffer gas cell allows for the preparation of cold, dense molecular ensembles. This source is combined with a feedback-stabilized Fabry-Pérot optical cavity and precision laser scheme to engineer strong coupling of individual rovibrational transitions in gas-phase molecules. The Weichman Lab will harness this apparatus to investigate how benchmark chemical processes, including bimolecular reactions, photodissociation, and photoisomerization, occur under cavity coupling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.