Shock-Tube Study of the Recombination Rate of Hydrogen Atoms with Oxygen Molecules

Measurements have been made of the rate of chain branching during the induction period of the H2–O2 reaction. Mixtures of H2–O2–CO–Ar were shock heated and the ``blue continuum'' emission from the O+CO→CO2+hv reaction was monitored using an end-on technique for sensitivity. Experiments performed at different densities were analyzed to yield the rate coefficient k4Ar=3.3×109 liters2 mole−2·sec−1 at 1100°K for the reactionH+O2+Ar→k4ArHO2+Ar.This value when combined with other literature values for k4Ar yields the temperature-dependent expressions k4Ar=(2.00±0.25)×109 [exp(870±70 cal/RT)] liter2 mole−2·sec−1 and k4Ar=(1.5±0.7)×1012T−0.88±0.08 liter2 mole−2·sec−1. In addition values of k1 for the reactionH+O2→k1OH+Owere obtained from the data between 975° and 2060°K and combined in the Arrhenius expression k1=9.54×1010 exp(−14.7 kcal/RT) liters mole−1·sec−1 accurate to ±20% over our range. A value for k2=1.98×109 liters mole−1·sec−1 (±40%) at 1500°K was obtained for the reactionO+H2→k2OH+H.The end-on technique is shown to be a useful tool to study recombination reactions involving only one free radical.