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| Titel |
Diode-laser measurements of CO₂-broadening coefficients in the ν₄ fundamental band of methane at room temperature |
| VerfasserIn |
Q. Delière, S. Robert, A. C. Vandaele, M. Lepère |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058548
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| Zusammenfassung |
| Methane is a minor component of our atmosphere, as well as of Jupiter,
Saturn, Uranus, Neptune and Mars. CH4 has been detected on Mars by many
studies1-2.
But the origin of methane is still uncertain, it can be internal processes like volcanic or
biological processes, or external like cometary impacts.
Self-broadening of CH43
and CH4 perturbed by N2, O2 and
Ar4-5
have already been measured. But they are only valid for Earth conditions. For atmospheric
observations of methane in the Martian atmosphere, we need parameters like broadening
coefficients due to carbon dioxide, the main constituent of the Martian atmosphere.
Using a tunable diode-laser spectrometer, we have measured CO2-broadening coefficients
of about 40 absorption lines of the P-, Q- and R- branches in the ν4 fundamental
band of methane, with J values ranging between 1 and 9. Each line was recorded
at room temperature (296 K) and for 4 different pressures, ranging from 8 to 50
mbar.
The experimental determination of CO2-broadening coefficient was performed by fitting
to the experimental profile of each line recorded at each pressure, a theoretical profile based
either on the Voigt or the Rautian-Sobel’Man models. The last one takes into account the
Dicke effect, a narrowing due to the molecular confinement.
Preliminary results will be presented and discussed. Impact on atmospheric investigations
on Mars will be addressed. |
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