EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Absorption Spectrum and Absolute Absorption Cross Sections of Acetylperoxy Radicals, CH3C(O)O2 in the near IR

Michael Rolletter1, Emmanuel Assaf2,3, Mohamed Assali2, Hendrik Fuchs1, and Christa Fittschen2
Michael Rolletter et al.
  • 1Forschungszentrum Jülich GmbH, IEK-8, Institute of Energy and Climate Research: Troposphere, Jülich, Germany (
  • 2Université Lille, CNRS, UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l’Atmosphère, Lille, France
  • 3now at: Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, Colorado, United States

Acetylperoxy radicals (CH3C(O)O2) play an important role in the tropospheric chemistry. They are produced by the photooxidation of most emitted biogenic non-methane hydrocarbons. Recent studies show that the CH3C(O)O2 + HO2 reaction, which is the most important tropospheric loss reaction of acetylperoxy radicals in regions that are dominated by biogenic emissions (low NO emissions), does not only lead to radical chain terminating products but can also regenerate OH. The competing secondary chemistry, e. g., the CH3C(O)O2 self-reaction, complicate kinetic measurements. The detection of acetylperoxy radicals in previous kinetic laboratory studies was mainly done in the UV region. However, the spectral overlap of different peroxy species in this region is prone to systematic errors in the quantitative detection. These complications can be avoided, if acetylperoxy radicals are detected by absorption in the near IR.

In our work, the near infrared CH3C(O)O2 spectrum was measured in the spectral ranges from 6094 cm-1 to 6180 cm-1 and 6420 cm-1 to 6600 cm-1. CH3C(O)O2 radicals were generated by pulsed photolysis of a acetaldehyde/Cl2/O2 mixture at 351 nm and were subsequently detected by time-resolved continuous-wave cavity ring-down spectroscopy (cw-CRDS). Experiments were done at 67 hPa in synthetic air and helium. The absorption cross sections of eight discrete absorption lines were determined relative to the absorption cross section of HO2, which has previously been reported.

How to cite: Rolletter, M., Assaf, E., Assali, M., Fuchs, H., and Fittschen, C.: The Absorption Spectrum and Absolute Absorption Cross Sections of Acetylperoxy Radicals, CH3C(O)O2 in the near IR, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5733,, 2020


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