Origin of OH Chemiluminescence during the Induction Period of the H2–O2 Reaction behind Shock Waves

Abstract

The intensity and the rate of increase of light emitted by the OH^{* 2}Σ⁺→²II(0–0) transition were studied during the induction period behind shock waves in 5% H₂—95% air mixture. Induction‐zone temperatures ranged from about 1000° to 1900°K, and the initial pressure was 10 Torr. A standard lamp was used to calibrate the optical system, so that photomultiplier signals could be transformed to OH^* concentration. The results are interpreted in terms of radical‐recombination reactions. It is found that OH^* is formed in the reaction H+O₂+H₂→H₂O+OH^* and is effectively quenched, in these experiments, only by water. The excitation process is an inefficient reaction, with an average rate constant of 2×10⁵ liter²/mole²·sec.