Rate coefficient for the reaction H+O2→OH+O: Results at high temperatures, 2000 to 5300 K

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Abstract
The tunable‐laser flash‐absorption technique has been used to study the high‐temperature behavior of the reaction H+O2→OH+O by monitoring the absorption of the hydroxyl radical. Sensitivity analysis of a detailed reaction mechanism shows that for fuel rich mixtures only two reactions are sensitive when hydroxyl is monitored: H2+M→2H+M and H+O2→OH+O. Rate coefficients for these reactions have been determined by least‐squares analysis of measured absorption profiles. For the rate of dissociation of H2 in krypton we obtain k1(T)=(8.86±0.88)×10−10 exp[−48321/T(K)] cm3 s−1 from 3450 to 5300 K. For the H+O2 reaction we combined our results with previous low temperature measurements and recommend k2(T)=(1.62±0.12)×10−10 exp[−(7474±122)/T(K)] cm3 s−1 from 960 to 5300 K. The uncertainties are at the 95% confidence level. Measured cross sections for rotational and vibrational energy transfer in O2 and OH have been used to show that relaxation effects do not influence the results. We compare our results to recent trajectory calculations. In addition, we calculate the rate of the reverse reaction, OH+O→H+O2, and compare it to trajectory and statistical adiabatic channel calculations. Finally, we point out that the first excited surface of the hydroperoxyl radical, 2A’, which correlates with H(2S)+O2(1Δg), may be needed to explain very high temperature results.

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