High temperature rate coefficient for the reaction of O( 3P) with H 2 obtained by the resonance absorption of O and H atoms

Abstract

The reaction of O( 3P) with H 2 has been studied behind reflected shock waves in the temperature range of 1713–3532K at total pressures of about 1.4–2.0 bar by Atomic Resonance Absorption Spectroscopy using mixtures of N 2O and H 2 highly diluted in Ar. The O atoms were generated by the fast thermal decomposition of N 2O and the reaction with H 2 was followed by monitoring the time dependent O and H atom concentrations in the postshock reaction zone. For the experimental conditions chosen, the measured O and H atom concentrations were primarily sensitive to the well-known N 2O dissociation and to the studied reaction and hence its rate coefficient could be deduced. The measured rate coefficient data are fitted by the least-squares method to obtain the following three parameter expression: K 4=3.72×10 6( T/ K) 2.17 exp(−4080 K/ T) cm 3 mol −18 −, which is in excellent agreement with the recent ab initio calculations for the rate coefficient of this reaction in the overlapping temperature range. The present result is also compared to the experimental results reported by earlier investigators.