Physical Chemistry Seminar: “New Experimental Platforms for Molecular Polaritonics” (Marissa L. Weichman, Princeton University)

Title: “New Experimental Platforms for Molecular Polaritonics” 

Abstract: Polaritons are hybrid light-matter states with unusual properties that arise from strong interactions between a molecular ensemble and the confined electromagnetic field of an optical cavity. Cavity-coupled molecules appear to demonstrate energetics, reactivity, and photophysics distinct from their free-space counterparts, but the mechanisms and scope of these phenomena remain open questions. I will discuss new experimental platforms that the Weichman Lab is developing to investigate molecular reaction dynamics under strong cavity coupling.

While polaritons are now well-established in solution-phase and solid-state systems, they had not been previously reported in isolated gas-phase molecules, where attaining sufficiently strong light-matter interactions is a challenge. We access the strong coupling regime in an intracavity cryogenic buffer gas cell optimized for the preparation of simultaneously cold and dense ensembles and report a proof-of-principle demonstration in gas-phase methane. We strongly cavity-couple individual rovibrational transitions and probe a range of coupling strengths and detunings. In ongoing work, we are harnessing this infrastructure as a testbed for fundamental studies of polariton physics and chemistry.

We are also searching for signatures of cavity-altered dynamics in benchmark condensed-phase systems. We use ultrafast transient absorption to examine intracavity dynamics in benchmark systems with the goal of better understanding exactly how and when reactive trajectories may be influenced by strong light-matter interactions. Time-permitting, I will touch on our work with solution-phase bimolecular reaction dynamics under vibrational strong coupling and excited state relaxation dynamics in thin films under electronic strong coupling.

Marissa L. Weichman
Assistant Professor of Chemistry, Princeton University

The Weichman Lab develops spectroscopic tools to probe the structure, dynamics, and chemical interactions of complex molecules and strongly interacting light-matter systems. Students and postdocs working with us gain technical expertise in ultrafast and precision spectroscopy, optical physics, instrument building, experiment design, and device fabrication, and will hone broadly applicable problem solving and data analytical skills.

You can read more about our work on the strong light-matter interactions and precision spectroscopy of complex molecules pages.