Atmospheric Reactions of Peroxy Radicals – Key Intermediates in Ozone Formation and Loss

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• Dr Geoff Tyndall, NCAR Colorado USA
• Tuesday 12 October 2010, 14:15-15:15
• Pfizer Lecture Theatre, Department of Chemistry.

If you have a question about this talk, please contact Dr Alex Archibald.

NOTE unusual DAY and LOCATION Joint with Physical Chemistry

Hydroperoxy radicals, HO2 , are central to atmospheric chemistry. In regions of the troposphere impacted by nitrogen oxides (NOx = NO + NO2) they are involved in ozone formation. On the other hand, in the remote troposphere (e.g., the marine boundary layer) or in the stratosphere they play an important role in ozone depletion. Closely related are the organic peroxy radicals, denoted as RO2 (where R represents an organic group). The chemistry of all these peroxy radicals in the atmosphere is coupled, via chain propagation steps which lead to their interconversion, and also by mutual loss processes.

At NCAR we study the reactions of organic compounds using two laboratory techniques. In the first, we use Fourier Transform Infrared Spectrometry to investigate the overall product yields. The second involves time-resolved IR laser spectroscopy to detect HO2 (hydroperoxy) radicals directly. Both systems can be temperature-regulated, to obtain data relevant to the entire troposphere. Coupled together, the two techniques offer a powerful means to study atmospheric oxidation mechanisms.

This talk will summarize some recent experimental studies of the chemistry of peroxy radicals under low-NOx conditions, including the self-reactions of HO2 radicals and their reactions with carbonyl species. Recent mechanistic developments related to peroxy radical regeneration in the atmosphere will also be discussed.

This talk is part of the Centre for Atmospheric Science seminars, Chemistry Dept. series.

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