Resonance absorption measurements of atom concentrations in reacting gas mixtures. VIII. Rate constants for O+H2→OH+H and O+D2→OD+D from measurements of O atoms in oxidation of H2 and D2 by N2O

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Abstract
Resonance absorption spectroscopy has been used to measure O atom concentration in shock treated H2–N2O–Ar and D2–N2O–Ar mixtures. Four compositions were studied over the temperature range 1919–2781 K for the H2‐containing mixtures and 2097–2481 K for those containing D2. Only a few elementary reactions exerted any appreciable influence on the total oxidation process so that the rate coefficients of those reactions could be deduced. Primary sensitivity under all conditions was to the rate coefficients of the reactions directly responsible for the formation and removal of oxygen atoms. We find O+H2→OH+H, k = 2.3E14 exp(−57.5 kJ/RT) cm3 mol−1 s−1 and O+D2→OD+D, k = 1.6E14 exp(−59.6 kJ/RT) cm3 mol−1 s−1. Under our conditions the reaction of H or D atoms with N2O was insignificant, in contrast to the observations of Dean at higher concentrations. The isotope effect for this reaction is close to 1.6 throughout our temperature range.