Speed-dependent broadening and line mixing in CH4 perturbed by Ar and N2 from multispectrum fits

Gabard, Tony

doi:10.1016/s0022-4073(99)00222-8

Cited by 79 publications

(92 citation statements)

References 26 publications

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“…It will be shown later that a multi-spectrum fit analysis 58 helps to overcome these problems. 59,60 We note that the choice of line profile not only affects the fit residuals but also has a strong effect upon the resulting fitted parameters. In Fig.…”

Section: Resultsmentioning

confidence: 99%

“…A solution to remove correlation between the Re(ν opt ) and a W parameters is to incorporate a multi-spectrum fit procedure 58 into the lineshape analysis. 44,59,60,63,64 Therefore, we performed simultaneous fits to the nine spectra from 6.5-28 kPa for the R(24) line and eight spectra from 6.5-24 kPa for the R(30) line with a few necessary constraints. First, the collisional widths and frequencies of optical collisions were constrained to be linear with pressure according to the relations Γ (p) = γ p and ν opt (p) = βp, where γ and β are the collisional broadening and collisional narrowing coefficients, respectively, fitted in the multi-spectrum analysis.…”

Section: Resultsmentioning

confidence: 99%

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Observations of Dicke narrowing and speed dependence in air-broadened CO2 lineshapes near 2.06 μm

Bui

Long

Cygan

et al. 2014

The Journal of Chemical Physics

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The line shape problem in the near-infrared spectrum of self-colliding CO 2 molecules: Experimental investigation and test of semiclassical models J. Chem. Phys. 130, 184306 (2009) Frequency-stabilized cavity ring-down spectroscopy was used to study CO 2 lineshapes in the (20013) ← (00001) band centered near 2.06 μm. Two rovibrational transitions were chosen for this study to measure non-Voigt collisional effects for air-broadened lines over the pressure range of 7 kPa-28 kPa. Lineshape analysis for both lines revealed evidence of simultaneous Dicke (collisional) narrowing and speed-dependent effects that would introduce biases exceeding 2% in the retrieved air-broadening parameters if not incorporated in the modeling of CO 2 lineshapes. Additionally, correlations between velocity-and phase/state changing collisions greatly reduced the observed Dicke narrowing effect. As a result, it was concluded that the most appropriate line profile for modeling CO 2 lineshapes near 2.06 μm was the correlated speed-dependent NelkinGhatak profile, which includes all of the physical effects mentioned above and leads to a consistent set of line shape parameters that are linear with gas pressure. © 2014 AIP Publishing LLC.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Observations of Dicke narrowing and speed dependence in air-broadened CO2 lineshapes near 2.06 μm

Bui

Long

Cygan

et al. 2014

The Journal of Chemical Physics

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“…The experimental values for the line positions and line broadening coefficients were taken from Refs. [34,42,47,52,80]. For the ν 4 band and the octad region, the perturber was in fact air [34,42], for which nitrogen contributes to about 80%.…”

Section: Applicationsmentioning

confidence: 99%

“…The 182 measurements range from 2916.2 cm −1 to 3122.8 cm −1 with angular momenta up to J ′′ = 13 [47,52,80]. Measurements for the ν 3 band Q branch [80] were re-examined to include line-mixing, Dicke narrowing and speed dependent line shapes in the analysis [52].…”

Section: The ν 3 Bandmentioning

confidence: 99%

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Line broadening coefficient calculations for methane perturbed by nitrogen

Gabard¹,

Boudon²

2010

Journal of Quantitative Spectroscopy and Radiative Transfer

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We report semiclassical line broadening calculations for methane perturbed by nitrogen at room temperature. For this, we have developed a symmetrized version of the Robert and Bonamy theory. The interaction potential was built from electrostatic (octopole and hexadecapole for methane, quadrupole for nitrogen) and atom-atom contributions. The relative (classical) trajectories of the molecules were computed in the frame of the usual parabolic model, through analytical formula. High orders of developments had to be used for the short range molecular interactions. As a consequence, a combination of symbolic computation and source code generation was employed to implement practical calculations. We have compared our calculations to the most recent experimental data available in the ν 4 band, the ν 3 band and the octad spectral region of methane.

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Spherical Top Theory and Molecular Spectra

Boudon

Champion

Gabard

et al. 2011

Handbook of High‐resolution Spectroscopy

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In this article, we present an overview of the present state of the art of the theory of high‐resolution spherical‐top spectra in the framework of the effective Hamiltonian approach. We describe the specific features of this class of molecules to explain the basic concepts of the theoretical methods used for the analysis (line positions and intensities) and the simulation of absorption (including pure rotation) and Raman spectra of such species. The non conventional formalism that we use is essentially based on irreducible tensor methods and is especially adapted to computational treatments and global analyses of complex interacting band systems. We give examples concerning mainly methane (CH 4 ) and sulfur hexafluoride (SF 6 ). The efficiency of these methods is not restricted to spherical tops, as they also apply to other molecular species or spectroscopic problems. We demonstrate this through recent developments including the modeling of the effects of collisions on line shapes, the modeling of rovibronic effects, as well as extensions to molecules with lower symmetry. The computer implementation of the methods is an integral part of the modeling. We conclude the article with an overview of the free access programs and databases developed in the Dijon group for spherical‐top molecules and some other species.

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Speed-dependent broadening and line mixing in CH4 perturbed by Ar and N2 from multispectrum fits

Cited by 79 publications

References 26 publications

Observations of Dicke narrowing and speed dependence in air-broadened CO2 lineshapes near 2.06 μm

Observations of Dicke narrowing and speed dependence in air-broadened CO2 lineshapes near 2.06 μm

Line broadening coefficient calculations for methane perturbed by nitrogen

Spherical Top Theory and Molecular Spectra

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