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Titel |
Laser Spectroscopic Study on Oxygen Isotope Effects in Ozone Surface Decomposition |
VerfasserIn |
Marco Minissale, Corinne Boursier, Hadj Elandaloussi, Yao Té, Pascal Jeseck, Christian Rouille, Thomas Zanon-Willette, Christof Janssen |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250135694
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Publikation (Nr.) |
EGU/EGU2016-16592.pdf |
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Zusammenfassung |
The isotope kinetics of ozone formation in the Chapman reaction [1]
O + O2 + M → O3 + M
(1)
provides the primary example for a chemically induced oxygen isotope anomaly and is
associated with large [2] and mass independent [3] oxygen isotope enrichments in the product
molecule, linked to a symmetry selection in the ozone formation kinetics [4–5]. The
isotopic composition of ozone and its transfer to other molecules is a powerful
tracer in the atmospheric and biogeochemical sciences [6] and serves as a primary
model for a possible explanation of the oxygen isotopic heterogeneity in the Solar
system [7–8]. Recently, the isotope fractionation in the photolytic decomposition
process
O3 + hν → O2 + O
(2)
using visible light has been studied in detail [9–10]. Much less is currently known about the
isotope fractionation in the dry deposition or in the gas phase thermal decomposition of
ozone
O3 + M → O2 + O +M.
(3)
Here we report on first spectroscopic studies of non-photolytic ozone decomposition
using a cw-quantum cascade laser at 9.5 μm. The concentration of individual ozone
isotopomers (16O3,16O16O17O, and 16O17O16O) in a teflon coated reaction cell is followed
in real time at temperatures between 25 and 150 ∘C. Observed ozone decay rates depend on
homogeneous (reaction (3)) processes in the gas phase and on heterogeneous reactions on
the wall. A preliminary analysis reveals agreement with currently recommended ozone decay
rates in the gas phase and the absence of a large symmetry selection in the surface
decomposition process, indicating the absence of a mass independent fractionation effect.
This result is in agreement with previous mass spectrometer (MS) studies on heterogeneous
ozone formation on pyrex [11], but contradicts an earlier MS study [12] on ozone surface
decomposition on pyrex and quartz. Implications for atmospheric chemistry will be
discussed.
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