A direct comparison of shock tube photolysis and pyrolysis methods in the determination of the rate coefficient for O + H2 → OH + H

Mixtures of NO, N2O, and H2 in Ar were shock-heated and photolyzed with an ArF excimer laser. Measurements of O-atom profiles using atomic resonance absorption spectroscopy (ARAS) permitted the determination of the rate coefficient for the reaction, O + H2 → OH + H, by two methods under near-identical conditions. The first used the pyrolysis of N2O as an O-atom source, and the second used the photolysis of NO as the O-atom source. The rate coefficients determined by the two methods are indistinguishable and are well represented in the temperature range 2120 to 2750 K by the expression 8.13(± 10%) × 1014 expBRET9540[±800/T (in K)]BRET1 cm3 mol−1 s−1. This rate coefficient agrees well with those previously reported in the literature.