Shock-Tube Study of OH Chemiluminescence in the Hydrogen–Oxygen Reaction

The exponential growth of $\mathrm{OH}{\mathrm{*(}}^2{\Sigma }^{+}{\to }^2\mathrm{\pi )}$ chemiluminescence was monitored during the induction period of the H₂–O₂ reaction in mixtures with $[{\mathrm{H}}_2\mathrm{]\hspace{0.17em}/\hspace{0.17em}[}{\mathrm{O}}_2\text{]\hspace{0.17em}=\hspace{0.17em}0.33}$ between 950° and 1150°K and at total gas densities between 0.50 and 1.1 × 10⁻² moles/liter. An end‐on technique with reflected shock waves provided the required sensitivity. The exponential growth constant for OH* emission was found to be a factor of 2 (2.07 ± 0.17) greater than that found for O–CO emission over the same range of conditions. This result shows that OH* is formed in a reaction between two products of the chain reaction and, together with other recent evidence, indicates that the reaction is H + O + (M)→OH* + (M). The use of OH* emission to study other combustion reactions is discussed.