Spectral line shapes for carbon dioxide in the 43-μm band

Cann, M. W. P.; Nicholls, R. W.; Roney, P. L.; Blanchard, Alain; Findlay, F. D.

doi:10.1364/ao.24.001374

Cited by 23 publications

(8 citation statements)

References 14 publications

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“…This assessment was primarily based on the HITRAN 9 (1992 and 1996) data set of emission lines complemented with some sample highresolution line-by-line calculations using CN189. 10 Candidate lines with strong emission strengths were favored in all the criteria except self-absorption. Here the two main criteria, isolation and self-absorption, are discussed.…”

Section: A Line Selectionmentioning

confidence: 99%

Performance evaluation of a thermal Doppler Michelson interferometer system

Mani

Dobbie

Scott³

et al. 2005

Appl. Opt.

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The thermal Doppler Michelson interferometer is the primary element of a proposed limb-viewing satellite instrument called SWIFT (Stratospheric Wind Interferometer for Transport studies). SWIFT is intended to measure stratospheric wind velocities in the altitude range of 15-45 km. SWIFT also uses narrowband tandem etalon filters made of germanium to select a line out of the thermal spectrum. The instrument uses the same technique of phase-stepping interferometry employed by the Wind Imaging Interferometer onboard the Upper Atmosphere Research Satellite. A thermal emission line of ozone near 9 microm is used to detect the Doppler shift due to winds. A test bed was set up for this instrument that included the Michelson interferometer and the etalon filters. For the test bed work, we investigate the behavior of individual components and their combination and report the results.

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Section: A Line Selectionmentioning

confidence: 99%

Performance evaluation of a thermal Doppler Michelson interferometer system

Mani

Dobbie

Scott³

et al. 2005

Appl. Opt.

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“…22 However, the quantum-mechanical description as well as experimental data show that real absorption lines are ''sub-Lorentzian'': roughly Lorentzian shaped around the line center but with weaker wings than the Lorentzian. 3, 23 The reason for this discrepancy is that the sudden collision approximation is valid only if ͉Ϫ i ͉⌬TӶ1, where ⌬T is a characteristic collision duration, the observed and i the line-center frequency. 24 To reproduce sub-Lorentzian profiles in our model, we have added an empirical collision duration mechanism to the stochastic sampling process.…”

Section: Finite Collision Durationmentioning

confidence: 99%

Time domain modeling of spectral collapse in high density molecular gases

Meinrenken

Gillespie

Macheret

et al. 1997

The Journal of Chemical Physics

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In many cases, the widely used matrix inversion approach to describe the spectral interference in collisionally perturbed molecular spectra is not feasible if the particular molecular interactions do not allow the sudden impact approximation (infinitely short collision duration). To overcome this problem, we present a time domain model that describes collisional broadening and narrowing phenomena without requiring the sudden approximation. The key element of the model is a Monte Carlo type sampling process to quantify the temporal autocorrelation of the molecular dipole moment. The spectrum is then obtained numerically via fast Fourier transform. The model does not require a frequency-dependent relaxation operator; the finite collision duration is simply an adjustable parameter in the time domain process. Our approach, which is generally applicable to any set of transition lines, is derived from concepts of both conventional quantum-mechanical and semiclassical theory of line interference. Coherent transfer effects from rotationally inelastic collisions are described as randomly occurring events which affect frequency, amplitude, and phase of the sampled oscillation. Effects of vibrational dephasing are included as well. To demonstrate its feasibility, we apply the model here to the 2.7 μ absorption spectrum of carbon dioxide diluted in high density air (ρ=43–485 amagat, T=297–754 K). The successful modeling of the experimental data, especially the full collapse of P and R branches at ultrahigh densities, accounts for interbranch mixing and for incoherent effects. The calculations make extensive use of the new Hitran (HITEMP) molecular database. Results include revised estimates for the collision duration of CO2 with nitrogen and oxygen at room temperature.

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“…In Part II we applied the near wing theory to the continuum beyond the band head of the 3 band of CO 2 near 4.2 m. As discussed in Part II the experimental results of Cann et al 15 were used for CO 2 broadened by N 2 at a temperature of 296 K. Reference 15 also gives results for O 2 and selfbroadening. These results are in the form of a form factor ͑⌬͒ which, for ⌬Ͼ50 cm Ϫ1 , is basically equivalent to ⌫͑͒ ͑as discussed in Part II͒.…”

Section: ͑42ј͒mentioning

confidence: 99%

Theory of spectral line shape. III. The Fano operator from near to far wing

Roney¹

1995

The Journal of Chemical Physics

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Extension of the quasistatic farwing line shape theory to multicomponent anisotropic potentials A nearwing correction to the quasistatic farwing line shape theory A far wing line shape theory and its application to the foreignbroadened water continuum absorption. III In this third part of a theory of spectral line shape, applicable to conditions of atmospheric transmission, an evaluation of the frequency dependence of the complete Fano collision operator has been made using the collision time theory developed earlier. This results in a considerable reduction of the terms in the Fano operator. An analysis of the spectral line wing shows that there are two different regimes: the near wing and the far wing. These regimes are demarcated by a turning point at a frequency displacement of kT/h. In the very far wing, beyond the turning point, the behavior of the Fano operator changes and the effects of binary collision overlap and photon absorption into the binary collision complex become important. The line wing behavior is corroborated qualitatively by experimental results for carbon dioxide near 4.2 m.

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Spectral line shapes for carbon dioxide in the 43-μm band

Cited by 23 publications

References 14 publications

Performance evaluation of a thermal Doppler Michelson interferometer system

Performance evaluation of a thermal Doppler Michelson interferometer system

Time domain modeling of spectral collapse in high density molecular gases

Theory of spectral line shape. III. The Fano operator from near to far wing

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