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@ARTICLE{Fuchs:276592,
      author       = {Fuchs, Hendrik and Tan, Zhaofeng and Hofzumahaus, A. and
                      Broch, S. and Dorn, H.-P. and Holland, F. and Künstler, C.
                      and Gomm, Sebastian and Rohrer, F. and Schrade, S. and
                      Tillmann, R. and Wahner, A.},
      title        = {{I}nvestigation of potential interferences in the detection
                      of atmospheric {RO}$_{x}$ radicals by laser-induced
                      fluorescence under dark conditions},
      journal      = {Atmospheric measurement techniques discussions},
      volume       = {8},
      number       = {11},
      issn         = {1867-8610},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2015-06946},
      pages        = {12475 - 12523},
      year         = {2015},
      abstract     = {Direct detection of highly reactive, atmospheric hydroxyl
                      radicals (OH) is widely accomplished by laser-induced
                      fluorescence (LIF) instruments. The technique is also
                      suitable for the indirect measurement of HO2 and RO2 peroxy
                      radicals by chemical conversion to OH. It requires sampling
                      of ambient air into a low pressure cell, where OH
                      fluorescence is detected after excitation by 308 nm laser
                      radiation. Although the residence time of air inside the
                      fluorescence cell is typically only on the order of
                      milliseconds, there is potential that additional OH is
                      internally produced, which would artificially increase the
                      measured OH concentration. Here, we present experimental
                      studies investigating potential interferences in the
                      detection of OH and peroxy radicals for the LIF instruments
                      of Forschungszentrum Jülich for nighttime conditions. For
                      laboratory experiments, the inlet of the instrument was
                      overflown by excess synthetic air containing one or more
                      reactants. In order to distinguish between OH produced by
                      reactions upstream of the inlet and artificial signals
                      produced inside the instrument, a chemical titration for OH
                      was applied. Additional experiments were performed in the
                      simulation chamber SAPHIR where simultaneous measurements by
                      an open-path differential optical absorption spectrometer
                      (DOAS) served as reference for OH to quantify potential
                      artifacts in the LIF instrument. Experiments included the
                      investigation of potential interferences related to the
                      nitrate radical (NO3, N2O5), related to the ozonolysis of
                      alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene,
                      α-pinene, limonene, isoprene), and the laser photolysis of
                      acetone. Experiments studying the laser photolysis of
                      acetone yield OH signals in the fluorescence cell, which are
                      equivalent to 0.05 × 106 cm−3 OH for a mixing ratio of 5
                      ppbv acetone. Under most atmospheric conditions, this
                      interference is negligible. No significant interferences
                      were found for atmospheric concentrations of reactants
                      during ozonolysis experiments. Only for α-pinene, limonene,
                      and isoprene at reactant concentrations which are orders of
                      magnitude higher than in the atmosphere artificial OH could
                      be detected. The value of the interference depends on the
                      turnover rate of the ozonolysis reaction. For example, an
                      apparent OH concentration of approximately 1 × 106 cm−3
                      is observed, if 5.8 ppbv limonene reacts with 600 ppbv
                      ozone. Experiments with the nitrate radical NO3 reveal a
                      small interference signal in the OH, HO2 and RO2 detection.
                      Dependencies on experimental parameters point to artificial
                      OH formation by surface reactions at the chamber walls or in
                      molecular clusters in the gas expansion. The signal scales
                      with the presence of NO3 giving equivalent radical
                      concentrations of 1.1 × 105 cm−3 OH, 1 × 107 cm−3 HO2,
                      and 1.7 × 107 cm−3 RO2 per 10 pptv NO3.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243) / HITEC - Helmholtz
                      Interdisciplinary Doctoral Training in Energy and Climate
                      Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-243 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/amtd-8-12475-2015},
      url          = {https://juser.fz-juelich.de/record/276592},
}