Resonance fluorescence method for kinetics of atomic reactions. Reactions of atomic hydrogen with olefins

Abstract

Using the technique of flash photolysis, absorption of Lyman-α radiation by H atoms and measurement of the subsequent Lyman alpha emission, the absolute rate constants for the reaction of hydrogen atoms with several olefins have been measured at room temperature. The method distinguishes hydrogen from deuterium atoms and can be used to measure either. The absolute limiting high-pressure rate constants at room temperature for the reactions H + C₂H₄,C₂D₄, and trans-2-butene, have been found to be approximately the same, k= 1·0 ±(15 %)× 10^–12 cm³ molecule^–1 sec^–1. The absolute rate constant for the reaction H + isobutene was k= 3·8 ±(15 %)× 10^–12 cm³ molecule^–1 sec^–1. For the reaction H + C₂H₄, a pressure effect on the bimolecular rate constant has been observed and this effect is discussed. The experimental method is described in detail since it appears to be the first of its kind and, in principle, generally applicable to the study of reactions of atoms other than hydrogen or deuterium.