Vibrational Spectroscopy and Dynamics of Reaction Intermediates

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Marsha Lester of the University of Pennsylvania is supported by the Chemical Structures, Dynamics and Mechanisms program to carry out a series of fundamental experimental studies of chemical reaction dynamics, many of which are based on chemical systems of significance in the atmosphere. The experiments utilize state-of-the-art spectroscopic and dynamical methods, but with the unique approach of initiating the studies from stabilized intermediates that lie along the reaction coordinate. Specifically, the planned studies focus on weakly bound species produced by association of OH and CN radicals with molecular partners on reactive potential energy surfaces. In each of these studies, fundamental or overtone excitation of the CN radical or hydride stretch of the intermediate will provide sufficient energy to initiate dynamics on a reactive potential energy surface. Experimental observables include spectroscopic parameters that characterize the reaction intermediates in high detail, for example molecular structures, vibrational frequencies, and thresholds for dissociation and/or reaction. In addition, dynamical information on dissociation and/or reaction dynamics will be obtained from the internal and/or kinetic energy release to products, yielding bond energies and enthalpies of formation for the intermediates. Experimental outcomes will be compared with theoretical calculations of the analogous properties derived from ab initio potential energy surfaces.In this project, young scientists at the undergraduate, graduate, and postdoctoral levels will participate in forefront scientific research, developing skills, experience, and confidence required to move into the scientific and technical workforce. The participants -- many of whom are women -- use technologically advanced laser equipment as they work on basic research projects, which are also relevant to broader issues in atmospheric chemistry.