State-Resolved Spectroscopy and Dynamics of Chemical Transients

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Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms - A Program of the Division of Chemistry, Prof. David J. Nesbitt from the University of Colorado is using state-of-the-art laser- and molecular beam-based methods to characterize the short-lived molecular structures ("chemical transients") that occur as reactants are transformed into products during chemical reactions. The overall goals of this experimental program are to develop tools to probe the molecular structure and reactivity of chemical transients. This project combines fluorescence microscopy and laser heating methods for studying both the kinetics and energetics of folding/unfolding of biologically-important species (e.g., nucleic acids, proteins, etc). Fluorescence is a process by which a molecule is exposed to light of a given wavelength, the molecule then gives off light of a different wavelength (the "color" of which is characteristic of that molecule). This research is expected to have impacts on a wide range of science, examining the chemical reactions of both living biological cells and the stars. The graduate students involved in this project are gaining experience in a wide range of tools (lasers and optics, electronics, and microscopy) that are highly valued in industry and advanced manufacturing. The results of these studies are also providing invaluable opportunities for graduate student participation in national professional meetings, outreach through scientific open houses, mentoring at the local high schools, as well as operation of the "CU Wizards" Science Outreach Program for elementary and middle school students.The overall goals of this experimental program are threefold: i) exploit quantum state resolved resonance enhanced multiphoton ionization (REMPI) and 3D velocity map imaging for the study of inelastic and hydrogen/deuterium (H/D) reaction dynamics at chemically tunable gas-self assembled monolayer interfaces, ii) develop and implement novel spectroscopic tools for probing quantum state-resolved evaporation/collision dynamics at the surface of high vapor pressure liquid (e.g., water) "microjets" and iii) utilize the powerful combination of time-resolved fluorescence microscopy and laser nano bathtub heating methods for fundamental chemical physics studies of temperature/viscosity dependent folding/unfolding of RNA at the single molecule level. Intellectual merits of this work derive from the variety of fundamental problems addressed involving highly reactive molecular transients, ranging from aerosol chemistry at the marine boundary layer and to novel proton coupled electron transfer (PCET) promoted H/D exchange at gas-liquid interfaces, to the conformational dynamics of single biomolecules. The broader impacts of this work involve training graduate and undergraduate students in state-of-the-art areas of chemical physics (e.g., quantum optics, pulsed and continuous wave lasers, plasmas, electronics, low noise photon detection, etc.), while furthering the discovery of fundamental new research knowledge.