The reaction of HO2 with acetyl peroxy radical, CH3C(O)O2, has been suggested to proceed via three channels [1]:(a) HO2 + CH3C(O)O2 ? CH3C(O)O2H + O2(b) HO2 + CH3C(O)O2 ? CH3C(O)OH + O3(c) HO2 + CH3C(O)O2 ? CH3C(O)O + OH + O2Channel (c) is of particular interest not only because of the lack of production of ozone, but also the formation of the hydroxyl radical, OH, a key oxidizing radical in the earth's atmosphere. The results from several independent studies [2,3,4] have shown that the branching ratio of (c) is close to 0.40. Although the results show strong evidence that channel (c) is a significant branch of the reaction of acetyl peroxy radical with HO2, all experiments were only done at room temperature (298 K) and none of the experiments used techniques that allowed for the measurement of either of the two reacting species. Another concern is that the overall reaction rates of acetyl peroxy radical with HO2 obtained by the experiments have shown large discrepancies. Furthermore, there is very little information on the temperature dependence of this reaction at upper troposphere temperatures. The results have led to upper and lower bound estimates by the JPL Data Evaluation panel that differ by almost an order of magnitude.The current study has employed a powerful method called Infrared Kinetic Spectroscopy (IRKS) for studying radical reactions. In the presented work, this technique is used to study the consumption of HO2 by CH3C(O)O2. Specifically, the kinetic rate constants of this reaction is determined as a function of temperature (220 to 298 K) and pressure (50 to 400 torr) by simultaneously measuring the disappearance of HO2 using near-IR spectroscopy and of CH3C(O)O2 using UV spectroscopy at a wavelength where HO2 does not absorb.[1] Hasson, A. S., Tyndall, G. S., Orlando, J. J. J. Phys. Chem. A, 2004, 108 (28), 5979�5989.[2] Crawford, M. A., Wallington, T. J., Szente, J. J., Maricq, M. M. J. Phys. Chem. A, 1999, 103 (3), 365�378.[3] Dillon, T. J. and Crowley, J. N. Atmos. Chem. Phys. Discuss., 2008, 8, 7111-7148.[4] Moortgat, G. K., Veyret, B., Lesclaux, R. Chem. Phy. Lett. 1989, 160 (4) 18, 443-447

Laboratory experiments of HO<sub>2</sub> reactions with peroxy radicals using infrared kinetic spectroscopy (IRKS)

248th National Meeting (2014)

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Laboratory experiments of HO2 reactions with peroxy radicals using infrared kinetic spectroscopy (IRKS)

Laboratory experiments of HO₂ reactions with peroxy radicals using infrared kinetic spectroscopy (IRKS)