Energy Exchange between Nuclei and Electrons: A Fundamental Chemical Question Addressed by Pure Electronic Rydberg Spectroscopy

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Robert Field of MIT is supported by the Experimental Physical Chemistry Program to develop experimental methods, theoretical models, and intuitive concepts by which the mechanisms for exchange of energy and angular momentum between an electron and a molecular cation may be characterized. Experiments will be carried out on small, gas phase molecules in highly excited electronic states with the goal of generating fundamental insights into the mechanisms and strength of its electron nuclear coupling that are germane to larger molecules, at all excitation energies, and in condensed phases. Multiplexed time-domain terahertz spectroscopy will be used in combination with multiple nanosecond dye laser excitation, in multi-laser schemes that will enable the probing of molecular Rydberg launch states under supersonic molecular beam conditions. Pure electronic spectroscopy studies of molecules of increasing spectroscopic and dynamical complexity (CaF, CaCl, and nitrogen dioxide) are expected to demonstrate the power of the combined nanosecond/femtosecond approaches to characterize, with a minimum of spectroscopic detective work, important electron--nuclear energy exchange mechanisms including their dependence on molecular geometries.Electron transport, electronic energy harvesting and disposal, and the making and breaking of chemical bonds all involve the exchange of energy between electrons and nuclei in molecules. Research outcomes from this effort have the potential to lead to important impacts in the understanding of energy couplings and flow in molecules. This project will enable effective research training of students. As well, Field has written an expanded and refocused textbook in molecular spectroscopy that is expected to be valuable for research and education applications.