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Abstract
The reactions of atomic chlorine and fluorine with several molecules of atmospheric and chemical interest have been studied at T = 295 K. In all cases the reactive halogen atoms were generated via the infrared multiphoton dissociation of selected precursor molecules. The reactions were monitored by analysis of the time dependent vibrational fluorescence of the product molecules produced by the exothermic reaction being studied.
The first study involved the reaction of chlorine and fluorine atoms with formaldehyde. SF(,6), CCl(,3)F and CClF(,3) were used as precursor molecules in the production of the desired halogen atoms. Isotope effects were determined for reaction with deuteroformaldehyde. Features of the reaction potential surface and the possible effects of vibrational energy within the reactant formaldehyde are discussed.
A real time competitive technique is presented in a subsequent study. The competition between deuterium and methane for atomic fluorine is investigated. The isotopic shift in vibrational fluorescence is sufficient to isolate the product signals of both reactions. It is shown both theoretically and experimentally that the total reaction rate of fluorine atoms is contained in either signal.
The final study makes use of this competitive technique and applies it to the reaction of atomic fluorine with nitrogen dioxide. The reaction of atomic fluorine with hydrogen is used as the diagnostic reaction. By measuring the rate as a function of nitrogen dioxide and buffer gas pressure the limiting low and high pressure rate constants for this third order reaction were obtained.
