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@ARTICLE{Carlsson:1005448,
      author       = {Carlsson, Philip T. M. and Vereecken, Luc and Novelli, Anna
                      and Bernard, François and Brown, Steven S. and Brownwood,
                      Bellamy and Cho, Changmin and Crowley, John N. and Dewald,
                      Patrick and Edwards, Peter M. and Friedrich, Nils and Fry,
                      Juliane and Hallquist, Mattias and Hantschke, Luisa and
                      Hohaus, Thorsten and Kang, Sungah and Liebmann, Jonathan and
                      Mayhew, Alfred W. and Mentel, Thomas and Reimer, David and
                      Rohrer, Franz and Shenolikar, Justin and Tillmann, Ralf and
                      Tsiligiannis, Epameinondas and Wu, Rongrong and Wahner,
                      Andreas and Kiendler-Scharr, Astrid and Fuchs, Hendrik},
      title        = {{C}omparison of isoprene chemical mechanisms under
                      atmospheric night-time conditions in chamber experiments:
                      evidence of hydroperoxy aldehydes and epoxy products from
                      {NO} 3 oxidation},
      journal      = {Atmospheric chemistry and physics},
      volume       = {23},
      number       = {5},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2023-01479},
      pages        = {3147 - 3180},
      year         = {2023},
      abstract     = {The gas-phase reaction of isoprene with the nitrate radical
                      (NO3) was investigated in experiments in the outdoor SAPHIR
                      chamber under atmospherically relevant conditions
                      specifically with respect to the chemical lifetime and fate
                      of nitrato-organic peroxy radicals (RO2). Observations of
                      organic products were compared to concentrations expected
                      from different chemical mechanisms: (1) the Master Chemical
                      Mechanism, which simplifies the NO3 isoprene chemistry by
                      only considering one RO2 isomer; (2) the chemical mechanism
                      derived from experiments in the Caltech chamber, which
                      considers different RO2 isomers; and (3) the FZJ-NO3
                      isoprene mechanism derived from quantum chemical
                      calculations, which in addition to the Caltech mechanism
                      includes equilibrium reactions of RO2 isomers, unimolecular
                      reactions of nitrate RO2 radicals and epoxidation reactions
                      of nitrate alkoxy radicals. Measurements using mass
                      spectrometer instruments give evidence that the new
                      reactions pathways predicted by quantum chemical
                      calculations play a role in the NO3 oxidation of isoprene.
                      Hydroperoxy aldehyde (HPALD) species, which are specific to
                      unimolecular reactions of nitrate RO2, were detected even in
                      the presence of an OH scavenger, excluding the possibility
                      that concurrent oxidation by hydroxyl radicals (OH) is
                      responsible for their formation. In addition, ion signals at
                      masses that can be attributed to epoxy compounds, which are
                      specific to the epoxidation reaction of nitrate alkoxy
                      radicals, were detected. Measurements of methyl vinyl ketone
                      (MVK) and methacrolein (MACR) concentrations confirm that
                      the decomposition of nitrate alkoxy radicals implemented in
                      the Caltech mechanism cannot compete with the ring-closure
                      reactions predicted by quantum chemical calculations. The
                      validity of the FZJ-NO3 isoprene mechanism is further
                      supported by a good agreement between measured and simulated
                      hydroxyl radical (OH) reactivity. Nevertheless, the FZJ-NO3
                      isoprene mechanism needs further investigations with respect
                      to the absolute importance of unimolecular reactions of
                      nitrate RO2 and epoxidation reactions of nitrate alkoxy
                      radicals. Absolute concentrations of specific organic
                      nitrates such as nitrate hydroperoxides would be required to
                      experimentally determine product yields and branching ratios
                      of reactions but could not be measured in the chamber
                      experiments due to the lack of calibration standards for
                      these compounds. The temporal evolution of mass traces
                      attributed to product species such as nitrate
                      hydroperoxides, nitrate carbonyl and nitrate alcohols as
                      well as hydroperoxy aldehydes observed by the mass
                      spectrometer instruments demonstrates that further oxidation
                      by the nitrate radical and ozone at atmospheric
                      concentrations is small on the timescale of one night
                      (12 h) for typical oxidant concentrations. However,
                      oxidation by hydroxyl radicals present at night and
                      potentially also produced from the decomposition of nitrate
                      alkoxy radicals can contribute to their nocturnal chemical
                      loss.},
      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:000946512800001},
      doi          = {10.5194/acp-23-3147-2023},
      url          = {https://juser.fz-juelich.de/record/1005448},
}