Shock-Tube Study of the Acetylene–Oxygen Reaction. I. CH(A 2Δ→X 2π) Chemiluminescence and CO Production during the Induction Period

The growths of CO infrared and CH(A 2Δ → X 2π) visible emission were monitored simultaneously during the induction period of shock-heated C2H2–O2–Ar gas mixtures. For both emissions, regions of exponential growth were observed, and the growth constants for the two phenomena were found to be the same in each experiment from 1320 to 2320°K using a gas mixture with the C2H2:O2:Ar proportions 5:10:985. Similar results were obtained with other gas mixtures. The results indicate that CH chemiluminescent emission observed during the induction period of the C2H2–O2 reaction is produced in a reaction first order in reaction intermediates. The use of this emission and its origin are discussed. Evidence is presented indicating that CO is produced with a “hot” nonthermal distribution of vibrational populations. Estimates of the degree of vibrational excitation of the CO produced during the induction period are made using measured vibrational relaxation times for CO and the exponential growth constants for CO production.