Theoretical Studies of State to State Chemistry

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The Theoretical and Computational Chemistry program is supporting Schatz's research program which is concerned with using computational methods to determine the rates of chemical reactions that are important in combustion and atmospheric chemistry. For certain kinds of reactions, the current generation of computers has opened up new opportunities for the use of theory to determine rate information at a level that is better than or competitive with experiment. A goal of the research program is therefore to develop theoretical methods (quantum and classical dynamics methods) that take advantage of the new computer power to characterize important reactions. Another component of this work is the representation of potential energy surfaces that determine the forces between the atoms while reaction takes place. Such surfaces have proven difficult to describe when simultaneous bond-breaking and bond-forming occurs, or when there are multiple reaction pathways. However the Schatz group has developed several techniques for representing these surfaces and the resulting surfaces have been widely used. The theoretical dynamics methods and reactive potential energy surfaces will together be used to study several specific chemical reactions of interest to the combustion and atmospheric kinetics community for the purpose of interpreting and predicting experiments. Planned studies are aimed at understanding the role of reagent vibrational excitation on chemical reactivity, including the importance of mode-specific chemistry; at characterizing reactions in which there is a change in electronic state while the reaction occurs (with emphasis on the influence of spin-orbit excitation on chemical reactivity); and in understanding reactions in which there is no reaction path that connects reagents and products. Other topics include the use of theory to understand the spectroscopy of transition states of chemical reactions, and the characterization of collisional relaxation rates that leads to the stabilization of reaction intermediates.