Near-Infrared Kinetic Spectroscopy of the HO_2 and C_2H_5O_2 Self-Reactions and Cross Reactions
Abstract
The self-reactions and cross reactions of the peroxy radicals HO_2 and C_2H_5O_2 and HO_2 were monitored using simultaneous independent spectroscopic probes to observe each radical species. Wavelength modulation (WM) near-infrared (NIR) spectroscopy was used to detect HO_2, and UV absorption monitored HO_2 and C_2H_5O_2. The temperature dependences of these reactions were investigated over a range of interest to tropospheric chemistry, 221−296 K. The Arrhenius expression determined for the cross reaction, k_2(T) = (6.01^(+1.95)_(−1.47)) × 10^(−13) exp((638 ± 73)/T) cm^3 molecules^(−1) s^(−1) is in agreement with other work from the literature. The measurements of the HO_2 self-reaction agreed with previous work from this lab and were not further refined.(1) The C_2H_5O_2 self-reaction is complicated by secondary production of HO_2. This experiment performed the first direct measurement of the self-reaction rate constant, as well as the branching fraction to the radical channel, in part by measurement of the secondary HO_2. The Arrhenius expression for the self-reaction rate constant is k_3(T) = (1.29^(+0.34)_(−0.27)) × 10^(−13)exp((−23 ± 61)/T) cm^3 molecules^(−1) s^(−1), and the branching fraction value is α = 0.28 ± 0.06, independent of temperature. These values are in disagreement with previous measurements based on end product studies of the branching fraction. The results suggest that better characterization of the products from RO_2 self-reactions are required.
Additional Information
© 2010 American Chemical Society. Published In Issue July 08, 2010; Article ASAP June 04, 2010; Received: December 23, 2009; Revised: April 29, 2010. This research was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). This work was supported by the NASA Upper Atmosphere Research and Tropospheric Chemistry Programs and the NASA Graduate Student Research Program (GSRP). The authors would like to thank Dave Natzic for extensive laboratory support and Dr. Lance Christensen and the Okumura group for many discussions. Note Added after ASAP Publication. This article posted ASAP on June 4, 2010. Tables 1 and 3 have been revised. The correction version posted on June 11, 2010.Additional details
- Eprint ID
- 19124
- DOI
- 10.1021/jp912129j
- Resolver ID
- CaltechAUTHORS:20100720-104159802
- NASA/JPL/Caltech
- NASA Graduate Student Research Fellowship
- Created
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2010-07-20Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field