15min:
RATE CONSTANTS AND DEUTERIUM KINETIC ISOTOPE EFFECTS FOR METHOXY RADICAL REACTING WITH NO2 AND O2.

J. CHAI, H. HU, T. S. DIBBLE, Department of Chemistry, College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210; G. S. TYNDALL, J. J. ORLANDO, Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado 80305.

Alkoxy radicals (RO) are important intermediates in the photooxidation of volatile organic compounds due to their great impacts on ozone formation and gas-particle partitioning of stable oxidation products. Methoxy radical (CH3O�) is the prototype for all alkoxy radicals. The absolute rate constants kNO2(T) for reaction of CH3O� and CD3O�with NO2 have been measured using laser flash photolysis to generate radicals and laser-induced fluorescence for time-resolved detection. The pressure and temperature dependence for kNO2 have been observed over the range 30-700 Torr and 250-335 K. This will be the first direct measurement of kNO2 for CH3O� near ambient pressure and the first ever for CD3O�.The relative rate constants kNO2/kO2(T) have been measured in an environmental chamber with FTIR detection. This combination enables the first determination of kO2 (T) for CH3O� and CD3O� for T < 298 K. The results will also help validate theoretical methods for studying alkoxy + O2 reactions, which are challenging for quantum chemistry.