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GEOPHYSICAL RESEARCH LETTERS, VOL. 28, NO. 20, PAGES 3863–3866, 2001

Accurate, Direct Measurements of OH Yields from Gas-Phase Ozone-Alkene Reactions Using an in situ LIF Instrument

Jesse H. Kroll

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA


Thomas F. Hanisco

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA


Neil M. Donahue

Departments of Chemistry and Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA


Kenneth L. Demerjian

Department of Earth and Atmospheric Sciences, and Atmospheric Sciences Research Center, SUNY-Albany, Albany, NY


James G. Anderson

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA


Abstract

We present direct, pressure-dependent measurements of OH yields from gas-phase ozone-alkene reactions, using the Harvard HOx instrument to obtain sensitive, accurate, and precise OH concentrations. As in previous studies from our laboratory, steady-state [OH] is measured by laser-induced fluorescence (LIF); here, the accurate LIF calibration allows us to present absolute OH yields for the first time. To calibrate our original LIF system, we measure yields from ozone plus tetramethylethylene (TME) as a function of pressure. The pressure dependence agrees with our previous results, so our yield measurements are now of comparable accuracy to those from indirect studies. Prompt, low-pressure yields agree well with 1 atm yields measured over longer timescales, confirming that much of the OH arises from decomposition of stabilized carbonyl oxides. We also explore the pressure dependence of yields from ethene, isobutene, and isoprene. Yields from isobutene and isoprene are pressure-dependent, consistent with the formation of substituted carbonyl oxides. We observe no pressure dependence of the OH yield from ozone + ethene, finding instead a constant yield of 14%, in line with most 1 atm studies but in contrast with the results of another pressure-dependent study.

Received 8 May 2001; accepted 1 August 2001.

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Citation: Kroll, J. H., T. F. Hanisco, N. M. Donahue, K. L. Demerjian, and J. G. Anderson (2001), Accurate, Direct Measurements of OH Yields from Gas-Phase Ozone-Alkene Reactions Using an in situ LIF Instrument, Geophys. Res. Lett., 28(20), 3863–3866.