Kinetics of the Species OH(A2Σ+), OH(X2Π and CH(X2Π) in the System C2H2/O/H

OH*(A 2Σ+) and OH(X2Π) concentration‐time‐profiles were measured in the gas phase reaction system C2H2/O/H at 2.66 mbar and 298 K in a discharge flow system for largely varying initial conditions. The well established chemiluminescence reaction CH + O2 → OH*(A2Σ+) + CO connects the experimental OH*(A2Σ+) concentrations to the concentrations of the intermediate CH(X 2Π) which is an important precursor of higher hydrocarbons. Computer analysis showed that the reaction CH2 + H → CH + H2 is the major CH formation reaction with a rate constant k4 of about 5 · 1013 cm3 mol−1 s−1. Reaction CH2 + O → CH + OH does not contribute significantly to either CH or OH formation. A rate constant k28 = 4.8 · 1010 cm3 mol−1 s−1 was obtained.