The effect of collisions on the Doppler broadening of spectral lines

Rautian, S. G.; Sobelman, Igor I.

doi:10.3367/ufnr.0090.196610a.0209

Cited by 183 publications

(67 citation statements)

References 2 publications

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“…A detailed study of molecular diffusion effects and collisional relaxation rates will be performed. We will be able to test, in our experimental conditions, the relevance of various theoretical models that include the velocity dependence of relaxation rates, such as the Galatry profile ("soft" collisions assumption [27]) or the Rautian profile ("hard" collisions assumption [29], actually introduced for the first time in spectroscopy by M. Nelkin and A. Ghatak in 1964 [28]). …”

Section: Resultsmentioning

confidence: 99%

“…In linear absorption spectroscopy and for an isotropic distribution of molecular velocities it can be shown that all transit effects are already included in the inhomogeneous Doppler broadening [25]. At high pressures, the LDM effect which results in a reduction of the Doppler width with pressure must be taken into account [26][27][28][29]. Finally, in our experiment two other effects that tend to broaden the line have to be considered: the unresolved hyperfine structure of the molecular transition and the modulations applied to the laser for detection purposes.…”

Section: Absorption Line Shapementioning

confidence: 98%

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Measurement of the Boltzmann constant by the Doppler broadening technique at a3.8×10−5accuracy level

Djerroud

Lemarchand

Gauguet

et al. 2009

Comptes Rendus. Physique

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In this article, we describe an experiment performed at the Laboratoire de physique des lasers and dedicated to an optical measurement of the Boltzmann constant k B . With the proposed innovative technique, determining k B comes down to an ordinary frequency measurement. The method consists in measuring as accurately as possible the Doppler absorption profile of a rovibrational line of ammonia in thermal equilibrium. This profile is related to the Maxwell-Boltzmann molecular velocity distribution along the laser beam. A fit of the absorption line shape leads to a determination of the Doppler width proportional to √ k B T and thus to a determination of the Boltzmann constant. The laser source is an ultra-stable CO 2 laser with a wavelength λ ≈ 10 µm. The absorption cell is placed in a thermostat, keeping the temperature at 273.15 K within 1.4 mK. We were able to measure k B with a relative uncertainty as small as 3.8 × 10 −5 , which represents an improvement of an order of magnitude for an integration time comparable to our previous measurement published in 2007. To cite this article: K. Djerroud et al., C. R. Physique 10 (2009). RésuméMesure de la constante de Boltzmann utilisant l'élargissement Doppler avec une incertitude relative de 3,8 × 10 −5 . Dans cet article, nous présentons l'expérience développée au Laboratoire de physique des lasers pour la mesure optique de la constante de Boltzmann k B . Cette nouvelle approche ramène la détermination de k B à une mesure de fréquence. L'expérience consiste à mesurer le plus exactement possible le profil d'absorption Doppler d'une raie de vibration-rotation de l'ammoniac à l'équilibre thermodynamique. Ce profil reflète la distribution de Maxwell-Boltzmann des vitesses moléculaires le long du faisceau laser. Une analyse de la forme de la raie d'absorption conduit à une détermination de l'élargissement Doppler, proportionnel à √ k B T , et donc à une mesure de la constante de Boltzmann. La mesure spectroscopique est réalisée à l'aide d'un laser à CO 2 ultra-stable de longueur d'onde λ ≈ 10 µm. La cellule d'absorption est placée dans un thermostat qui permet de contrôler la température autour de 273,15 K avec une incertitude de 1,4 mK. Ces mesures nous ont conduit récemment à une détermination de k B avec une incertitude relative de 3,8 × 10 −5 . Cela représente, pour des temps de mesure comparables, un gain d'un ordre de grandeur par rapport à notre précédente mesure publiée en . Pour citer cet article : K. Djerroud et al., C. R. Physique 10 (2009).

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Section: Resultsmentioning

confidence: 99%

Section: Absorption Line Shapementioning

confidence: 98%

Measurement of the Boltzmann constant by the Doppler broadening technique at a3.8×10−5accuracy level

Djerroud

Lemarchand

Gauguet

et al. 2009

Comptes Rendus. Physique

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“…Nevertheless, such a Lennard-Jones potential may give rise to quite good values of pressure broadening and shift coefficients. Taking into account the estimated value (about 1.5 x 10 -3 cm -1 ) of the Dicke narrowing and the fact that the correlation between velocity-changing and dephasing collisions [4,18,42,22] may lead to complete reduction of the Dicke effect [18], we can conclude that the observed decrease in the Doppler width should not be caused by the Dicke narrowing effect.…”

Section: J1• the Voigt Analysismentioning

confidence: 99%

“…a convolution of a Gaussian profile arising from the thermal motion of emitters with Maxwellian distribution of velocities and a Lorentzian profile describing the collisional broadening. If, however, the speed-changing collision and the correlation between collisions and thermal motion are taken into account, then as was shown [1][2][3][4][5][6][7][8][9] the resultant profile may deviate significantly from the Voigt profile and give rise to an asymmetric line shape. The *Department.…”

Section: Introductionmentioning

confidence: 99%

Speed-Dependent Effects on the 748.8 nm Ne Self-Broadened Line

et al. 1999

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Profiles of the self-broadened 748.8 nm Ne line emitted from a glow discharge in neon in the pressure range between 0.8 and 100 Tr were measured using an improved experimental setup with pressure-scanned Fabry-Perot interferometer. First, line profiles were analysed using an ordinary Voigt procedure which yielded the Doppler widths decreasing with the increase in neon pressure. Using a speed-dependent Voigt profile it was shown that for the 748.8 nm line the correlation between the Doppler and collisional broadening plays an important role. However, the values of the pressure broadening and shift coefficients determined by the speed-dependent Voigt analysis were found to be only slightly different from those obtained by the ordinary Voigt analysis. A systematic error in the determination of perturber concentration in onr previous investigation was corrected.

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“…It has been shown in [72] that the real contour of a line must have less intense tails than is the case in the Lorentz'contour. The intensity in the tails decreases proportionally with the fourth power of the frequency, not its square as the dispersion contour implies.…”

mentioning

confidence: 99%

Propagation of Visible and Infrared Waves in the Atmosphere (Rasprostranenie Vidimykh i Infrakrasnykh Voln v Atmosfere)

Zuev¹

1972

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The effect of collisions on the Doppler broadening of spectral lines

Cited by 183 publications

References 2 publications

Measurement of the Boltzmann constant by the Doppler broadening technique at a3.8×10−5accuracy level

Measurement of the Boltzmann constant by the Doppler broadening technique at a3.8×10−5accuracy level

Speed-Dependent Effects on the 748.8 nm Ne Self-Broadened Line

Propagation of Visible and Infrared Waves in the Atmosphere (Rasprostranenie Vidimykh i Infrakrasnykh Voln v Atmosfere)

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