Low Energy Ion-Molecule Reactions

Abstract

Grant DE-FG02-88ER13849 and predecessor grants Project SummaryThis project has been dedicated to elucidating the dynamics of elementary ion-molecule reactions at collision energies between 0.1 and 5 eV under single collision conditions in crossed beams. The long-standing objective of this project has been to probe the potential energy surfaces for elementary gas phase reactions. The studies we have conducted throughout a sustained period of Department of Energy support have been directed at testing theory in benchmark systems, with the long term goal of extracting useful dynamical insights that can be transferred to the complex environment of hydrocarbon combustion, where energy disposal in polyatomic systems plays a critical role.To support these objectives, crossed ion beam-neutral beam reactive scattering experiments have been being performed with the goal of using product quantum state distributions, energy disposal measurements, and state-resolved angular distributions to extract dynamical information on collision mechanics and features of the potential energy surfaces mediating ion-molecule reactions. These studies allow us to test and validate dynamical models describing chemical reactivity. Measurements of energy and angular distributions of the reaction products with vibrational state resolution provide the key data for these studies. The studies have been designed to foster interactions between theory and experiment, in which benchmark systems are probed experimentally with the most sophisticated techniques available and which 3 are also amenable to computations of structural and dynamical features at a high level. In addition to studying these benchmark systems, we have also studied more complex systems in which one can still apply the underlying "small system" concepts, gaining important insights into reactivity by probing critical subspaces of the full potential surface that governs the dynamics. 4 Summary of Key ResultsThe work we have accomplished during the tenure of this research breaks down into the