Professor Stephen J. Klippenstein at the Department of Chemistry, Case Western Reserve University, is supported by a grant from the Theoretical and Computational Chemistry Program at NSF for the development of theoretical approaches and the application of these approaches to the study of barrierless reactions. These reactions can be viewed as unimolecular dissociation reactions for which there is no barrier to the reverse recombination process. The research under this grant is focused on three topics: (1) The description of the interaction energies between the reacting fragments. (2) The determination of the density of states, especially in the region of the transition state. And, (3) the study of energy flow processes in the reaction, especially as this can be used to evaluate statistical models of reaction kinetics. Detailed comparisons of the results obtained from these studies are being made with experimental results and with other theoretical results in order to obtain an enhanced understanding of reaction dynamics. Accurate descriptions of the kinetics of barrierless associations and the reverse dissociations are of the utmost importance for the modelling of a variety of gas phase chemistries including those occuring in combustion, atmospheric, and interstellar environments. An important objective of the work supported by this grant is to improve the ability to interpret and to predict properties of these barrierless reactions.
