Comparison and analysis of rotationally inelastic collision models describing the Q-branch collapse at high density

Bulgakov, Yu. I.; Storozhev, A.V.; Strekalov, M.L.

doi:10.1016/0301-0104(93)80185-c

Cited by 19 publications

(3 citation statements)

References 31 publications

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“…In addition, to obtain satisfactory agreement with experiment, the authors in Ref. 27 have taken an unusually large energy relaxation cross section of E ϭ35 Å 2 , larger than any other value obtained previously.…”

Section: ͑11͒mentioning

confidence: 77%

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Collision effects in nitrogen and methane coherent anti-Stokes Raman isotropic Q-branch spectra at high densities

Ridder

Suvernev

Dreier

1996

The Journal of Chemical Physics

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Using coherent anti-Stokes Raman spectroscopy ͑CARS͒ the spectral shift and width of the collisionally narrowed Q-branch structures of nitrogen and the 1 symmetric stretch vibration in methane were investigated at high densities. The gas samples either contained the pure substance or, for the case of nitrogen and methane, were diluted with argon, methane and carbon monoxide or argon and nitrogen, respectively, in the pressure range 50-2000 bar and at temperatures between 300 and 700 K. The simultaneous recording of spectra at ambient conditions ensured a frequency measurement accuracy of 0.07 cm Ϫ1 . Contributions to the line shapes and frequency shifts are determined that originate from narrowing of the rotational structure and from vibrational dephasing in nitrogen, methane, and its mixtures. The results are compared with quasiclassical calculations of the band shape and shift to determine thermally averaged collision cross sections for energy relaxation and vibrational dephasing as a function of temperature. In the investigated density regime, for nitrogen the band shape is dominated by collisional narrowing. The peak position of the band does not strongly depend on composition of the sample and the maximum red shift of the Raman frequency diminishes with increasing temperature. For methane at densities above 50 amagat effects from rotational relaxation are no longer detectable and dephasing collisions are dominant. In addition to vibration-translation relaxation, vibrational energy transfer is an important process for line broadening at high densities. The frequency shift of the Q-band strongly depends on mixture composition and temperature.

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Section: ͑11͒mentioning

confidence: 77%

“…Our results for nitrogen have to be compared with a recent work by Bulgakov et al, 27 who introduced a nonlinear effective density dependence through an excluded volume effect. They were able to describe the nitrogen isotropic Q-branch width, in agreement with the experimental results from Lavorel et al 5 to liquid-like densities ͑800 amagat͒.…”

Section: ͑11͒mentioning

confidence: 87%

Collision effects in nitrogen and methane coherent anti-Stokes Raman isotropic Q-branch spectra at high densities

Ridder

Suvernev

Dreier

1996

The Journal of Chemical Physics

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“…The application of eq 8 to Q-branch narrowing has a long history. , Recently, renewed attempts were made by several authors. ,,− They were quite effective, especially when the cross-correlation term in eq 5 was assumed to be zero …”

Section: Nonlinear Density Dependence Of Relaxation Timesmentioning

confidence: 99%

Rotational Relaxation in Fluid Nitrogen: An Ambiguity in the Interpretation of the Q-Branch Collapse?

Temkin

Steele

1996

J. Phys. Chem.

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A molecular dynamics simulation of nitrogen at 295 K and at densities ranging from 400 to 1000 amagat has been carried out. Relaxation times which give the rotational contribution to isotropic Raman Q-branch halfwidths have been determined from the simulations. A comparison of these simulations with experiment leads to the conclusions that (1) extreme motional narrowing theory is applicable to the calculation of bandwidths for densities not less than 700 amagat; (2) the nonlinear density dependence of rotational energy relaxation times should be incorporated in the scaling laws to obtain dependable calculations of bandwidths;(3) by rescaling molecular dynamics results of Levesque et al. (J. Chem. Phys. 1980, 72, 2744 for liquid nitrogen we show that negative rotational relaxation-vibrational dephasing cross correlation is not negligible for fluid nitrogen at high density and 295 K; and (4) calculations of the collision frequency for a model ensemble of hard spheres with density-dependent diameters (Ben-Amotz, D.; Hershbach, D. R. J. Phys. Chem. 1993, 97, 2295 yield good estimates for the density dependence of the simulated relaxation times.

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Rotational coherent anti-Stokes Raman spectroscopy (CARS) in nitrogen at high pressures (0.1-44 MPa): experimental and modelling results

Bood¹,

Bengtsson²,

Dreier

2000

J. Raman Spectrosc.

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Comparison and analysis of rotationally inelastic collision models describing the Q-branch collapse at high density

Cited by 19 publications

References 31 publications

Collision effects in nitrogen and methane coherent anti-Stokes Raman isotropic Q-branch spectra at high densities

Collision effects in nitrogen and methane coherent anti-Stokes Raman isotropic Q-branch spectra at high densities

Rotational Relaxation in Fluid Nitrogen: An Ambiguity in the Interpretation of the Q-Branch Collapse?

Rotational coherent anti-Stokes Raman spectroscopy (CARS) in nitrogen at high pressures (0.1-44 MPa): experimental and modelling results

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