15min:

A. C. NOELL, L. S. ALCONCEL, D. J. ROBICHAUD AND M. OKUMURA, Department of Chemistry, California Institute of Technology, Pasadena, CA 91125; S. P. SANDER, Jet Propulsion Laboratory, Pasadena, CA 91109.

Reactions between RO₂ and HO₂ are important in the gas phase oxidation of volatile organics in the atmosphere. The rate constants for the reactions of HO₂ + C₂H₅O₂, and C₂H₅O₂ + C₂H₅O₂ were measured using a novel approach to radical radical reactions that employs two independent spectroscopic probes. HO₂ was monitored at 6638.2 cm^-1 using near-IR diode laser WM spectroscopy, and C₂H₅O₂ was monitored at 250 nm using UV absorption. Experiments were run under conditions relevant to the upper troposphere (221-298 K and 50-400 Torr). Measurements of the rate constants for both reactions as well as a measurement of the branching fraction leading to the alkoxy channel of the C₂H₅O₂ self reaction will be discussed. Preliminary results are: k_HC = (6.4\pm1.4)×10^-13 cm³ molec^-1 s^-1 Exp((601\pm120)/ T ), k_CC = (1.10\pm0.20)× 10^-13 cm³ molec^-1 s^-1 independent of temperature, and a branching fraction of 0.32\pm0.13.