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@PHDTHESIS{Fuchs:55628,
      author       = {Fuchs, Hendrik},
      title        = {{M}easurement of {P}eroxy {R}adicals using
                      {L}aser-{I}nduced {F}luorescence {T}echnique},
      volume       = {72},
      issn         = {1433-5530},
      school       = {Humboldt-Universität Berlin},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-55628},
      isbn         = {3-89336-467-6},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Umwelt /
                      Environment},
      pages        = {VI, 141 S.},
      year         = {2006},
      note         = {Record converted from VDB: 12.11.2012;
                      Humboldt-Universität Berlin, Diss., 2006},
      abstract     = {Peroxy radicals are produced during the photochemical
                      degradation of volatile organic compounds (VOCs) in the
                      atmosphere. They are part of the catalytic radical cycle
                      initiated by hydroxyl radicals (OH) in which hydrocarbons
                      are oxidized leading to the removal of pollutants. The
                      reaction of peroxy radicals with nitrogen monoxide (NO) in
                      conjunction with the photochemical cycling of nitrogen
                      dioxide (NO$_{2}$) and nitrogen monoxide leads to the
                      formation of ozone (O$_{3}$). This process is the major
                      photochemical source for ozone in the troposphere concerning
                      the local as well as the global ozone budget. A new method
                      for the measurement of atmospheric hydroperoxy and organic
                      peroxy radical concentrations (HO$_{2}$ and RO$_{2}$) was
                      developed using the successive conversion of RO$_{2}$ and
                      HO$_{2}$ to OH radicals which are detected by laser-induced
                      fluorescence (LIF). The detection system consists of two
                      differentially pumped chambers. Ambient air is sampled
                      through a nozzle into the first chamber in which the
                      pressure is reduced from atmospheric pressure to 25
                      $\textit{hPa}$. An excess of NO and CO is added downstream
                      of the inlet, leading to the conversion of RO$_{2}$ to
                      HO$_{2}$ radicals. The pressure is further reduced in the
                      second chamber to 3.5 $\textit{hPa}$. HO$_{2}$ is
                      transformed to OH by the reaction with a further excess of
                      NO. The detection of OH radicals is achieved by time delayed
                      gated photon counting after resonant excitation of the
                      OH-fluorescence at 308$\textit{nm}$ (A$^{2}$Σ$^{+}$ -
                      X$^{2}$Π). The sensitivity of the system is calibrated
                      using a radical source in which OH and HO$_{2}$ radicals are
                      produced by water photolysis. In order to calibrate the
                      RO$_{2}$ sensitivity, a hydrocarbon is mixed to the
                      calibration gas. OH reacts quantitatively with the
                      hydrocarbon resulting in the formation of RO$_{2}$ radicals.
                      The typical detection limit of the LIF system for peroxy
                      radicals is 2·10$^{6}$ $\textit{cm}^{−3}$ to 7·10$^{6}$
                      $\textit{cm}^{−3}$ (0.1 $\textit{pptv}$ to 0.3
                      $\textit{pptv}$) for an integration time of 30 $\textit{s}$
                      and for a signal-to-noise-ratio of two. The estimated
                      accuracy is 10\% which is mainly determined by the
                      uncertainty of the calibration. Unlike in peroxy radical
                      amplifier (PERCA) instruments which are used for measuring
                      HO$_{2}$+RO$_{2}$-radical concentrations, only a weak
                      dependence of the sensitivity on the water vapor content in
                      the sampled air is found which can be explained by humidity
                      dependent quenching of the OH fluorescence. The instrument
                      was characterized in laboratory measurements. The results
                      agree with analytic and numerical calculations investigating
                      the reaction kinetics of the RO$_{2}$ conversion process.
                      Measurements of peroxy radicals were validated by
                      simultaneous measurements of the new LIF instrument and an
                      established measurement technique (Matrix Isolation and
                      Electron Spin Resonance, MIESR) in experiments at the
                      atmosphere simulation chamber SAPHIR. The SAPHIR chamber
                      allows to investigate chemical processes under controlled
                      atmospheric conditions. First ambient air measurements of
                      peroxy radicals were performed during the international
                      field campaign HOxCOMP in July 2005 showing reasonable
                      diurnal profiles.},
      cin          = {ICG-II},
      ddc          = {333.7},
      cid          = {I:(DE-Juel1)VDB48},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK406},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/55628},
}