US-France Cooperative Research: Kinetics and Dynamics of Refractory Radical Reactions

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The award will support collaborative research between Dr. Arthur Fontijn, Rensselaer Polytechnic Institute, and Dr. G. Dorth, Laboratory of Photophysics and Photochemistry, University of Bordeaux, France. The objective of the research is to carry out crossed molecular beam experiments, which will allow the investi- gators to study isolated chemical reactions and to determine precisely the threshold energy level necessary for the reactions to proceed. Knowledge of gas-phase reactions of radicals of refractory elements is of fundamental interest, and is required for the modeling of practical problems including many aspects of combustion, chemical vapor deposition and upper atmospheric chemistry. Yet, because of the difficulties inherent in obtaining adequate concentrations of such species, their reactions have been measured by few investigators and most studies made concern near room- temperature kinetics. In the proposed program, selected reactions of "refractory radicals" will be studied by two complementary approaches. Their kinetics will be measured in the 300 - 1800 K range by the unique HTFFR ( high-temperature fast-flow reactor) and/or HTP (high-temperature photochemistry) techniques at Rensselaer. Their dynamics will be investigated by the equally unique pulsed crossed supersonic molecular beams (with laser evaporation of the refractory species) technique in Bordeaux. The excitation functions from the dynamics measurements will be converted to rate coefficient versus temperature plots using absolute values from the kinetics work and thus allow, for single channels, extrapolation of the kinetic results to wider temperature ranges. The kinetic work involves reactants in thermal equilibrium excitation states, while the dynamics studies yield state-to-state information. Differences in results can reveal important second channels, such as are attributable to vibrational excitation. The accurate determination of the reaction energetics in Bordeaux will provide an invaluable aid to the interpretation of the Rensselaer results for reactions, such as those of the alkaline earth atoms, where these data are not adequately known.