Vibrational Coherence Probes of Polariton Photochemistry

With support from the Chemical Structure and Dynamics (CSD) program in the Division of Chemistry, Professor Andrew Musser of Cornell University is using a new spectroscopic approach based on molecular vibrations to understand how light-matter interactions can tune the properties of molecules non-synthetically. When molecules are placed in carefully designed photonic structures that trap light, they often behave in surprising ways, forming new ‘polariton’ states that exhibit changes in charge and energy transport or chemical reactivity.

These effects could transform photochemistry and catalysis, but they remain poorly understood and hard to predict. Professor Musser and his students will apply cutting-edge ultrafast laser-based techniques to a library of optical cavities in order to watch molecules inside move in real time and determine how their motions, which are fundamentally linked to reactive properties, are altered by the light-matter coupling.

By isolating the unique dynamics of the polaritons, the team will establish how such photonic structures can be used to redirect molecular photochemistry without having to synthesize new molecules. Their studies could lead to new fundamental understanding of strong light-matter interactions and inspire new developments using polaritons for improved photocatalysts or light-emitting devices.

The team will train multiple undergraduates in spectroscopy research and develop middle-school outreach programs focused on the nature of light and light-matter interactions.

A core premise behind the idea of polariton-controlled (photo)chemistry is that strong light-matter coupling distorts molecular potential energy surfaces. This effect has never been detected. This project will use a sensitive ultrafast vibrational technique—impulsive vibrational spectroscopy—to capture the signatures of excited polaritons by launching and tracking coherent vibrational wavepackets on the ground- and excited-state potential energy surfaces.

By incorporating optical control pulses, the team will distinguish any unique polaritonic wavepacket dynamics and infer the associated changes to the potential energy landscape. Comparing these measurements over systematically tuned microcavities, the team will develop empirical guidelines for how to maximize such polaritonic distortions and thereby alter the dynamics of coherent photochemical processes.

The results will lay the photophysical foundation and identify the key photonic and materials control knobs to dial in polaritonic effects. This work will open an avenue to develop polaritonic (photo)chemical reactors that exploit light-matter interactions to redirect traditional reaction pathways, creating a valuable resource for the synthetic chemistry community.

Students who participate in this project learn an array of relevant for high technology professions in the molecular sciences or photonics.

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.