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@ARTICLE{Vereecken:890523,
author = {Vereecken, L. and Carlsson, P. T. M. and Novelli, A. and
Bernard, F. and Brown, S. S. and Cho, C. and Crowley, J. N.
and Fuchs, H. and Mellouki, W. and Reimer, David and
Shenolikar, J. and Tillmann, R. and Zhou, L. and
Kiendler-Scharr, A. and Wahner, A.},
title = {{T}heoretical and experimental study of peroxy and alkoxy
radicals in the {NO} 3 -initiated oxidation of isoprene},
journal = {Physical chemistry, chemical physics},
volume = {23},
number = {9},
issn = {1463-9076},
address = {Cambridge},
publisher = {RSC Publ.},
reportid = {FZJ-2021-01010},
pages = {5496-5515},
year = {2021},
abstract = {The initial stages of the nitrate radical (NO3) initiated
oxidation of isoprene, in particular the fate of the peroxy
(RO2) and alkoxy (RO) radicals, are examined by an extensive
set of quantum chemical and theoretical kinetic
calculations. It is shown that the oxidation mechanism is
highly complex, and bears similarities to its OH-initiated
oxidation mechanism as studied intensively over the last
decade. The nascent nitrated RO2 radicals can interconvert
by successive O2 addition/elimination reactions, and
potentially have access to a wide range of unimolecular
reactions with rate coefficients as high as 35 s−1; the
contribution of this chemistry could not be ascertained
experimentally. The chemistry of the alkoxy radicals derived
from these peroxy radicals is affected by the nitrate
moiety, and can lead to the formation of nitrated epoxy
peroxy radicals in competition with isomerisation and
decomposition channels that terminate the organic radical
chain by NO2 elimination. The theoretical predictions are
implemented in the FZJ-NO3-isoprene mechanism for
NO3-initiated atmospheric oxidation of isoprene. The model
predictions are compared against peroxy radical (RO2) and
methyl vinyl ketone (MVK) measurements in a set of
experiments on the isoprene + NO3 reaction system performed
in the SAPHIR environmental chamber (IsopNO3 campaign). It
is shown that the formation of NO2 from the peroxy radicals
can prevent a large fraction of the peroxy radicals from
being measured by the laser-induced fluorescence (ROxLIF)
technique that relies on a quantitative conversion of peroxy
radicals to hydroxyl radicals. Accounting for the relative
conversion efficiency of RO2 species in the experiments, the
agreement between observations and the theory-based
FZJ-NO3-isoprene model predictions improves significantly.
In addition, MVK formation in the NO3-initiated oxidation
was found to be suppressed by the epoxidation of the
unsaturated RO radical intermediates, allowing the
model-predicted MVK concentrations to be in good agreement
with the measurements. The FZJ-NO3-isoprene mechanism is
compared against the MCM v3.3.1 and Wennberg et al. (2018)
mechanisms.},
cin = {IEK-8},
ddc = {540},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {211 - Die Atmosphäre im globalen Wandel (POF4-211)},
pid = {G:(DE-HGF)POF4-211},
typ = {PUB:(DE-HGF)16},
pubmed = {33650589},
UT = {WOS:000627550700037},
doi = {10.1039/D0CP06267G},
url = {https://juser.fz-juelich.de/record/890523},
}