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| Titel |
Accurate measurements of ozone absorption cross-sections in the Hartley band |
| VerfasserIn |
J. Viallon, S. Lee, P. Moussay, K. Tworek, M. Petersen, R. I. Wielgosz |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 3 ; Nr. 8, no. 3 (2015-03-13), S.1245-1257 |
| Datensatznummer |
250116214
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| Publikation (Nr.) |
 copernicus.org/amt-8-1245-2015.pdf |
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| Zusammenfassung |
| Ozone plays a crucial role in tropospheric chemistry, is the third largest
contributor to greenhouse radiative forcing after carbon dioxide and methane
and also a toxic air pollutant affecting human health and agriculture.
Long-term measurements of tropospheric ozone have been performed globally
for more than 30 years with UV photometers, all relying on the absorption of
ozone at the 253.65 nm line of mercury. We have re-determined this
cross-section and report a value of 11.27 x 10−18 cm2 molecule−1
with an expanded relative uncertainty of 0.86% (coverage
factor k= 2). This is lower than the conventional value currently in use
and measured by Hearn (1961) with a relative difference of 1.8%, with
the consequence that historically reported ozone concentrations should be
increased by 1.8%. In order to perform the new measurements of
cross-sections with reduced uncertainties, a system was
set up to generate pure ozone
in the gas phase together with an optical system based on a UV laser with
lines in the Hartley band, including accurate path length measurement of the
absorption cell and a careful evaluation of possible impurities in the ozone
sample by mass spectrometry and Fourier transform infrared spectroscopy. This resulted in new measurements of absolute values of ozone
absorption cross-sections of 9.48 x 10−18, 10.44 x 10−18
and 11.07 x 10−18 cm2 molecule−1, with
relative expanded uncertainties better than 0.7%, for the wavelengths
(in vacuum) of 244.06, 248.32, and 257.34 nm respectively. The cross-section
at the 253.65 nm line of mercury was determined by comparisons using a
Standard Reference Photometer equipped with a mercury lamp as the light
source. The newly reported value should be used in the future to obtain the
most accurate measurements of ozone concentration, which are in closer
agreement with non-UV-photometry based methods such as the gas phase
titration of ozone with nitrogen monoxide. |
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