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@ARTICLE{Albrecht:857601,
      author       = {Albrecht, Sascha R. and Novelli, Anna and Hofzumahaus,
                      Andreas and Kang, Sungah and Baker, Yare and Mentel, Thomas
                      and Wahner, Andreas and Fuchs, Hendrik},
      title        = {{M}easurements of hydroperoxy radicals
                      $({HO}\<sub\>2\</sub\>)$ at atmospheric concentrations using
                      bromide chemical ionization mass spectrometry},
      journal      = {Atmospheric measurement techniques discussions},
      volume       = {amt-2018-195},
      issn         = {1867-8610},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2018-06586},
      pages        = {1 - 19},
      year         = {2018},
      abstract     = {Hydroxyl and hydroperoxy radicals are key species for the
                      understanding of atmospheric oxidation processes. Their
                      measurement is challenging due to their high reactivity,
                      therefore very sensitive detection methods are needed.
                      Within this study, the measurement of hydroperoxy radicals
                      (HO2) using chemical ionization combined with an high
                      resolution time of flight mass spectrometer (Aerodyne
                      Research Inc.) employing bromide as primary ion is
                      presented. The 1σ limit of detection of
                      4.5×107moleculescm−3 for a 60s measurement is below
                      typical HO2 concentrations found in the atmosphere. The
                      detection sensitivity of the instrument is affected by the
                      presence of water vapor. Therefore, a water vapor dependent
                      calibration factor that decreases approximately by a factor
                      of 2 if the water vapor mixing ratio increases from 0.1 to
                      $1.0\%$ needs to be applied. An instrumental background most
                      likely generated by the ion source that is equivalent to a
                      HO2 concentration of 1.5±0.2×108moleculescm−3 is
                      subtracted to derive atmospheric HO2 concentrations. This
                      background can be determined by overflowing the inlet with
                      zero air. Several experiments were performed in the
                      atmospheric simulation chamber SAPHIR at the
                      Forschungszentrum Jülich to test the instrument performance
                      by comparison to the well-established laser-induced
                      fluorescence (LIF) technique for measurements of HO2. A high
                      linear correlation coefficient of R2=0.87 is achieved. The
                      slope of the linear regression of 1.07 demonstrates the good
                      absolute agreement of both measurements. Chemical conditions
                      during 15 experiments allowed testing the instrument’s
                      behavior in the presence of atmospheric concentrations of
                      H2O, NOx and O3. No significant interferences from these
                      species were observed. All these facts are demonstrating a
                      reliable measurement of HO2 by the chemical ionization mass
                      spectrometer presented.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243)},
      pid          = {G:(DE-HGF)POF3-243},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/amt-2018-195},
      url          = {https://juser.fz-juelich.de/record/857601},
}