Search results for "METHANE"
showing 10 items of 1763 documents
New measurements and global analysis of chloromethane in the region from 0 to 1800cm−1
2003
Abstract New high resolution Fourier transform spectra of pure 12CH335Cl and 12CH337Cl isotopomers of chloromethane have been recorded in Wuppertal covering the region from 600 to 3800 cm−1. New rotational transitions within the v2=1, v5=1, and v3=2 states have been measured at Lille. A first global analysis of the lower four band systems of the molecule (700–1800 cm−1) is reported. The model was based on an effective Hamiltonian and dipole moment expressed in terms of irreducible tensor operators. A common set of 125 effective hamiltonian parameters (sixth order) has been adjusted to fit simultaneously some 11 000 IR data for each of the isotopomers including 153 mm wave data for 12 CH3 35…
Line strengths of the ν2 + ν3 and ν3 − ν2 bands of methane (12CH4)
1992
Abstract The individual linestrengths of two related bands of 12 CH 4 , ν 2 + ν 3 near 4545 cm −1 and ν 3 − ν 2 near 1484 cm −1 , were measured with accuracies of 3% and 5%, respectively. In the analysis, an eight-term expansion of the dipole moment through second order was required to fit the strengths of transitions up to J ′ = 10 in ν 2 + ν 3 and J ′ = 12 in ν 3 − ν 2 and to explain the considerable perturbations observed. Application of this model reduced the rms deviations from 68% (zero-order) to 6.3% with the 248 selected lines of ν 2 + ν 2 and from 37% to 5.8% with 186 lines of ν 3 − ν 2 . The integrated bandstrengths for the two bands, respectively, are 1.84(5) and 0.0085(4) cm −2 …
Corrigendum to "Titan's surface and atmosphere from Cassini/VIMS data with updated methane opacity" [Icarus 226 (2013) 470-486]
2013
0019-1035/$ see front matter 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.icarus.2013.07.015 DOI of original article: http://dx.doi.org/10.1016/j.icarus.2013.05.033 ⇑ Corresponding author. Address: LESIA, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France. Fax: +33 145072806. E-mail address: bruno.bezard@obspm.fr (B. Bezard). 1 Present address: Foundation ‘‘La main a la pâte’’, Montrouge, France. M. Hirtzig , B. Bezard a,⇑, E. Lellouch , A. Coustenis , C. de Bergh , P. Drossart , A. Campargue , V. Boudon , V. Tyuterev , P. Rannou , T. Cours , S. Kassi , A. Nikitin , D. Mondelain , S. Rodriguez , S. Le Mouelic g
New ground state constants of 12CH335Cl and 12CH337Cl from global polyad analysis
2005
Abstract A global analysis of the infrared spectrum of chloromethane involving the ground state and the 13 vibrational states lying up to 2600 cm −1 was recently achieved using high resolution Fourier transform spectra of pure isotopomers. More than 20 000 transitions (cold and hot bands) for each isotopomer 12 CH 3 35 Cl and 12 CH 3 37 Cl have been assigned and fitted with a standard deviation of about 3 × 10 −4 cm −1 close to the experimental precison. As part of this global effort, improved ground state constants up to sextic centrifugal distortion terms have been determined for each isotopomer taking advantage of the numerous allowed and perturtation-allowed transitions simultaneously …
Analysis of the CH3D Nonad from 2000 to 3300 cm−1
2002
As part of the simultaneous analysis of line positions and intensities of the first two polyads of monodeuterated methane, the results achieved for the 3 to 5 mu m region are reported.
A large-area transition radiation detector
1990
Abstract The construction and the operation of a large-area transition radiation detector (TRD) for the NA31 experiment at CERN are described. The TRD incorporates several novel features for stabilizing the detector response. The density of the gas mixture (xenon+helium+methane) in the detection chambers is matched to the carbon dioxide gas in the surrounding radiators by tuning the helium concentration to avoid a hydrostatic pressure difference, which would deform the chamber walls. The chamber pressure is continuously regulated by computer control to maintain it to within 1 μbar of the radiator pressure. The gas gain of each of the four chambers is regulated to better than 0.2% by changin…
Argon-broadened line parameters in the nu3 band of 12CH4
1997
International audience; Prompted by improved measurements of collisional line shapes in the nu3 band P, Q and R branches of 12CH4, we have performed semi-classical line broadening calculations for methane perturbed by argon. We have used the theoretical approach developed by Robert and Bonamy as an extension of the well-known Anderson-Tsao-Curnutte theory. The semi-classical theory as reformulated here is shown to fully account for the tetrahedral symmetry of methane type molecules. The variation of argon-broadened linewidth coefficients in the nu3 band of 12CH4 with the branch, J, symmetry and energy level fine structure is discussed.
MeCaSDa and ECaSDa: Methane and ethene calculated spectroscopic databases for the virtual atomic and molecular data centre
2013
Abstract Two spectroscopic relational databases, denoted MeCaSDa and ECaSDa, have been implemented for methane and ethene, and included in VAMDC (Virtual Atomic and Molecular Data Centre, http://portal.vamdc.eu/vamdc_portal/home.seam ). These databases collect calculated spectroscopic data from the accurate analyses previously performed for the electronic ground state of methane, ethene, and some of their isotopologues: 12CH4, 13CH4, and 12C2H4. Both infrared absorption and Raman scattering lines are included. The polyad structures are reported and the transitions are precisely described by their energy, their intensity and the full description of the lower and upper states involved in the …
New assignments in the 2μm transparency window of the 12CH4 Octad band system
2013
Abstract This paper reports new assignments of rovibrational transitions of 12 CH 4 bands in the range 4600–4887 cm −1 which is usually referred to as a part of the 2 μm methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603 m absorption path length and pressures of 1, 7 and 34 hPa for samples of natural abundance CH 4 provided new measurements of 12 CH 4 lines. Older spectra for 13 CH 4 (90% purity) from JPL with 73 m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to th…
The Intensities of Methane in the 3–5 μm Region Revisited
2001
The analysis of the linestrengths of the infrared spectrum of methane (12 and 13) in the 3-5 µm region has been revisited on the basis of new measurements from Fourier transform spectra recorded at Kitt Peak under various optical densities. A simultaneous fit of these new data with previously reported tunable difference-frequency laser data has been done. An effective transition moment model in tensorial form up to the third order of approximation within the Pentad scheme has been used. The standard deviations achieved are very close to the experimental precision: 3 and 1.5%, respectively, for the two sets of data for the (12)CH(4) molecule, representing a substantial improvement with respe…