QLC: EAGER: Control of Quantum Dynamics and Catalysis Using Molecular Polaritonics

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Chemists routinely study how light interacts with molecules. Optical spectroscopy is an important tool in the characterization of molecular structure and chemical reactions. In recent years there has been a growing interest in an unusual twist of optical spectroscopy: if the container holding the molecules is modified to include two parallel mirrors, light that enters the container will interact with the sample molecules, and also reflect back and forth between the mirrors. If the dimensions of the container just right (a few microns, where a micron is one millionth of a meter), the mixing of light and molecules creates a new kind of particle. These new light-matter hybrids are called "polaritons," and their behavior can be manipulated by changing the dimensions of the cavity or the wavelength of light. In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Kevin Kubarych of the University of Michigan and his students are combining microcavities and advanced laser-based optical spectroscopy to study the behavior of polaritons. They are interested in how polaritons respond to changes in light exposure, and whether the actual chemical reactivity of the molecular parts of the polaritons is different from normal molecules, and whether their reactivity can be controlled simply by changing the dimensions of the container. A potential outcome of this research is the improved efficiency and economy of chemical reactions, perhaps including industrial catalytic processes and those relevant to solar energy conversion.Vibrational strong coupling between molecular vibrational states and cavity modes leads to energy shifted states that have hybrid molecular and optical character. Mode-selective coupling offers the promise to externally modulate chemical structure and energetics, which can be used to manipulate relaxation dynamics, such as excited state charge transfer and ground electronic state electrocatalysis. This proposal aims to (1) greatly expand the scope of coordination complexes coupled to microcavities to develop fundamental understanding of polaritons and their relaxation (vibrational energy relaxation and redistribution, as well as spectral diffusion and coherence transfer); (2) employ polariton-modulated excited state charge transfer in molecular ?forks? to control the movement of electronic wavepackets with polaritonic bridging vibrations; (3) combine microcavities with electrochemistry using thin gold layers as both cavity mirrors and electrodes for electrochemistry and electrocatalysis. The students involved in this project are gaining invaluable experience in ultrafast spectroscopy, quantum dynamics, chemical reaction dynamics and electrocatalysis. Improvements in practical electrocatalysis stand to dramatically enhance our ability to reduce CO2 while generating useful fuels.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.