| Abstract
| - The motivation for the present study comes from the preceding paper where it is suggested that accepted rateconstants for OH + NO2 → NO + HO2 are high by ∼2. This conclusion was based on a reevaluation of heatsof formation for HO2, OH, NO, and NO2 using the Active Thermochemical Table (ATcT) approach. Thepresent experiments were performed in C2H5I/NO2 mixtures, using the reflected shock tube technique andOH-radical electronic absorption detection (at 308 nm) and using a multipass optical system. Time-dependentprofile decays were fitted with a 23-step mechanism, but only OH + NO2, OH + HO2, both HO2 and NO2dissociations, and the atom molecule reactions, O + NO2 and O + C2H4, contributed to the decay profile.Since all of the reactions except the first two are known with good accuracy, the profiles were fitted byvarying only OH + NO2 and OH + HO2. The new ATcT approach was used to evaluate equilibrium constantsso that back reactions were accurately taken into account. The combined rate constant from the present workand earlier work by Glaenzer and Troe (GT) is kOH+NO2 = 2.25 × 10-11 exp(−3831 K/T) cm3 molecule-1 s-1,which is a factor of 2 lower than the extrapolated direct value from Howard but agrees well with NO + HO2→ OH + NO2 transformed with the updated equilibrium constants. Also, the rate constant for OH + HO2suitable for combustion modeling applications over the T range (1200−1700 K) is (5 ± 3) × 10-11 cm3molecule-1 s-1. Finally, simulating previous experimental results of GT using our updated mechanism, wesuggest a constant rate for kHO2+NO2 = (2.2 ± 0.7) × 10-11 cm3 molecule-1 s-1 over the T range 1350−1760K.
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