Theoretical and Experimental Determination of the Rate Constant of the Nonadiabatic Chemiluminescent Reaction H + O + N2 = OH* + N2.

The electronically nonadiabatic reaction of preassociation H + O + N₂ ↔ OH^* + N₂ is the main channel of formation of electronically excited chemiluminescent OH^* molecules during the oxidation of hydrogen in mixtures with a high content of nitrogen, e.g., during the combustion of hydrogen in air. For this reaction, within the framework of the combined theoretical and experimental approach with the use of the earlier results of quantum-chemical calculations for the rate constant of the elementary process H + O → OH^* in the limit of high pressures and experimental data on OH^* glow in N₂-diluted H₂/O₂ mixtures (including those obtained in this work), a physically substantiated dependence of the rate constant on temperature and pressure has been obtained for a broad range of thermodynamic parameters (T = 200–4000 K and p = 10^–3–10² atm). It has been shown that the found rate constant is in reasonable agreement with the existing results of measurements in both shock tubes and flames, with the rate constant in the process under study in a nitrogen buff er gas (M = N₂) turning out to be nearly 1.3–1.8 times lower (at atmospheric pressure) than for M = Ar. It has been noted that in interpreting measurements of the temporal intensity profiles of OH^* emission collected from the entire combustible volume (from the end of a shock tube), taking account of the self-absorption of emission on combustion products is substantial. [ABSTRACT FROM AUTHOR]