Journal
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
Volume 111, Issue 9, Pages 1117-1129Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jqsrt.2010.02.006
Keywords
Methane; Synchrotron radiation; Far infrared; Line intensities; Titan
Categories
Funding
- ANR [BLAN08-2_321467]
- Bourgogne Franche-Comte
- CNRS [3152]
- Fonds de la Recherche Scientifique (FRS-FNRS, Belgium)
- Action de Recherches Concertees of the Communaute francaise de Belgique
Ask authors/readers for more resources
As a tetrahedral molecule, methane has no permanent dipole moment. Its spectrum, however, displays faint absorption lines in the THz region, due to centrifugal distorsion effects. This is important for planetary applications since this region is used to measure methane concentration in some planetary atmospheres, in particular on Titan. Up to now, all measurements relied either on some old low resolution infrared absorption spectra, or on high resolution Stark measurements for low J values only. Even if these results have been reexamined recently [Wishnow EH, Orton GS, Ozier I. Gush HP. The distorsion dipole rotational spectrum of CH4: a low temperature far-infrared study.J Quant Spectrosc Radiat Transfer 2007:103:102-17], it seemed highly desirable to obtain much more precise laboratory data. The high-intensity synchrotron radiation, combined with a 151.75 +/- 0.1 m optical path in a White cell and a Bruker IFS 125 HR FTIR spectrometer at the AILES beamline of SOLEIL, enabled us to record this very weak spectrum at high resolution for the first time. Spectra were obtained in the 50-500 cm(-1) wavenumber range at 296K and 9.91, 20, 50 and 100 mbar with a resolution of 0.00074, 0.00134, 0.0034 and 0.0067 cm(-1) (FWHM of the sinc function), respectively. The rotational clusters are fully resolved and the good signal-to-noise ratio has enabled precise measurements of transition intensities (92 cold band lines and 96 Dyad-Dyad hot band lines, with normal abundance intensities in the range 2 x 10(-26)-1 x 10(-24) cm(-1) /(mol cm(-2))), yielding an accurate determination of the dipole moment derivatives. Such results should allow a better determination of CH4 concentration in planetary objects. (C) 2010 Elsevier Ltd. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available