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@ARTICLE{Zhao:893415,
      author       = {Zhao, Defeng and Pullinen, Iida and Fuchs, Hendrik and
                      Schrade, Stephanie and Wu, Rongrong and Acir, Ismail-Hakki
                      and Tillmann, Ralf and Rohrer, Franz and Wildt, Jürgen and
                      Guo, Yindong and Kiendler-Scharr, Astrid and Wahner, Andreas
                      and Kang, Sungah and Vereecken, Luc and Mentel, Thomas F.},
      title        = {{H}ighly oxygenated organic molecule ({HOM}) formation in
                      the isoprene oxidation by ${NO}\<sub\>3\</sub\>$ radical},
      journal      = {Atmospheric chemistry and physics},
      volume       = {21},
      number       = {12},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-02739},
      pages        = {9681 - 9704},
      year         = {2021},
      abstract     = {Highly oxygenated organic molecules (HOM) are found to play
                      an important role in the formation and growth of secondary
                      organic aerosol (SOA). SOA is an important type of aerosol
                      with significant impact on air quality and climate. Compared
                      with the oxidation of volatile organic compounds by ozone
                      (O3) and hydroxyl radical (OH), HOM formation in the
                      oxidation by nitrate radical (NO3), an important oxidant at
                      nighttime and dawn, has received less attention. In this
                      study, HOM formation in the reaction of isoprene with NO3
                      was investigated in the SAPHIR chamber (Simulation of
                      Atmospheric PHotochemistry In a large Reaction chamber). A
                      large number of HOM, including monomers (C5), dimers (C10),
                      and trimers (C15), both closed-shell compounds and
                      open-shell peroxy radicals (RO2), were identified and were
                      classified into various series according to their formula.
                      Their formation pathways were proposed based on the peroxy
                      radicals observed and known mechanisms in the literature,
                      which were further constrained by the time profiles of HOM
                      after sequential isoprene addition to differentiate first-
                      and second-generation products. HOM monomers containing one
                      to three N atoms (1–3N-monomers) were formed, starting
                      with NO3 addition to carbon double bond, forming peroxy
                      radicals, followed by autoxidation. 1N-monomers were formed
                      by both the direct reaction of NO3 with isoprene and of NO3
                      with first-generation products. 2N-monomers (e.g.,
                      C5H8N2On(n=7–13), C5H10N2On(n=8–14)) were likely the
                      termination products of C5H9N2On•, which was formed by the
                      addition of NO3 to C5-hydroxynitrate (C5H9NO4), a
                      first-generation product containing one carbon double bond.
                      2N-monomers, which were second-generation products,
                      dominated in monomers and accounted for $∼34 \%$ of all
                      HOM, indicating the important role of second-generation
                      oxidation in HOM formation in the isoprene + NO3
                      reaction under our experimental conditions. H shift of
                      alkoxy radicals to form peroxy radicals and subsequent
                      autoxidation (“alkoxy–peroxy” pathway) was found to be
                      an important pathway of HOM formation. HOM dimers were
                      mostly formed by the accretion reaction of various HOM
                      monomer RO2 and via the termination reactions of dimer RO2
                      formed by further reaction of closed-shell dimers with NO3
                      and possibly by the reaction of C5–RO2 with isoprene. HOM
                      trimers were likely formed by the accretion reaction of
                      dimer RO2 with monomer RO2. The concentrations of different
                      HOM showed distinct time profiles during the reaction, which
                      was linked to their formation pathway. HOM concentrations
                      either showed a typical time profile of first-generation
                      products, second-generation products, or a combination of
                      both, indicating multiple formation pathways and/or multiple
                      isomers. Total HOM molar yield was estimated to be
                      $1.2 \%+1.3\%−0.7\%,$ which corresponded to a SOA yield
                      of $∼3.6 \%$ assuming the molecular weight of C5H9NO6 as
                      the lower limit. This yield suggests that HOM may contribute
                      a significant fraction to SOA yield in the reaction of
                      isoprene with NO3.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {2111 - Air Quality (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2111},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000668601000003},
      doi          = {10.5194/acp-21-9681-2021},
      url          = {https://juser.fz-juelich.de/record/893415},
}