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

The exponential growth of OH*(2Σ+→2π) chemiluminescence was monitored during the induction period of the H2–O2 reaction in mixtures with [H2] / [O2] = 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.