Influence of the line-shape model on the spectroscopic determination of the Boltzmann constant

Cygan, A.; Lisak, D.; Trawiński, R. S.; Ciuryło, R.

doi:10.1103/physreva.82.032515

Cited by 50 publications

(46 citation statements)

References 53 publications

(78 reference statements)

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“…Clearly, the use of realistic description of collisions in line shape calculations is crucial for different applications such as the spectroscopic determination of the Boltzmann constant, 4,5,46,86 testing quantum treatment of molecules with high precision (in particular, line intensities) 49 or search for new fundamental physical effects. 87,88 Comparing the descriptions of the velocity-changing collisions given by various models (see Sec.…”

Section: Line Profilementioning

confidence: 99%

Velocity-changing collisions in pure H2 and H2-Ar mixture

Wcisło

Tran

Kassi

et al. 2014

The Journal of Chemical Physics

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We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self-and Ar-perturbed H 2 . We demonstrate that the billiardball (BB) approximation of the H 2 -H 2 and H 2 -Ar potentials gives an accurate description of the velocitychanging collisions. The BB model results are compared with ab initio classical molecular dynamics simulations (CMDS). It is shown that the BB model correctly reproduces not only the principal properties such as frequencies of velocity-changing collisions or collision kernels, but also other characteristics of H 2 -H 2 and H 2 -Ar gas kinetics like rate of speed-changing collisions. Finally, we present line-shape measurement of Q (1) line of the first overtone band of self-perturbed H 2 . We quantify the systematic errors of line-shape analysis caused by the use of oversimplified description of velocity-changing collisions. These conclusions will have significant impact on recent rapidly developing ultra-accurate metrology based on Doppler-limited spectroscopic measurements like Doppler-width thermometry, atmosphere monitoring, Boltzmann constant determination or transition position and intensity determination for fundamental studies.

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Section: Line Profilementioning

confidence: 99%

Velocity-changing collisions in pure H2 and H2-Ar mixture

Wcisło

Tran

Kassi

et al. 2014

The Journal of Chemical Physics

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“…As have been intensively studied in Refs. [16,37,38,39,40,41], Table 1. Gaussian widths (FWHM, in MHz) and corresponding spectroscopy temperatures (in K) derived from the fitting of the spectra using different line profile models and parameters.…”

Section: Statistical Uncertainty and Reproducibilitymentioning

confidence: 99%

“…Moreover, by measuring the spectra at different pressures and extrapolate the results to the zero-pressure limit, it is possible to reduce the systematic error of the Doppler width to less than 1 ppm. [38] Moretti et al have estimated that the uncertainty due to line profile models is about 15 ppm for their measurements with sample pressures at the 10 2 Pa level. [16] Since the sample pressure used in our CRDS measurement is about 1/100 of that used in conventional direct absorption studies, we expect that the uncertainty could be potentially reduced to less than 1 ppm.…”

Section: Statistical Uncertainty and Reproducibilitymentioning

confidence: 99%

“…The reported DBT results are mostly based on direct absorption spectroscopy of different atomic or molecular transitions, including Rb [17], NH 3 [12,13,14], CO 2 [15], H 2 O [16], C 2 H 2 [18,19], and O 2 [20]. Molecular lines, as ro-vibrational transitions in most studies, have very narrow natural line width, and the saturation effect is also negligible.…”

Section: Introductionmentioning

confidence: 99%

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Doppler Broadening Thermometry Based on Cavity Ring-Down Spectroscopy

Hu¹

2014

Proceedings of the 69th International Symposium on Molecular Spectroscopy

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Abstract. A Doppler broadening thermometry (DBT) instrument is built based on cavity ring-down spectroscopy (CRDS) for precise determination of the Boltzmann constant. Compared with conventional direct absorption methods, the high-sensitivity of CRDS allows to reach a satisfied precision at lower sample pressures, which reduces the influence due to collisions. By recording the spectrum of C 2 H 2 at 787 nm, we demonstrate a statistical uncertainty of 6 ppm (part per million) in the determined linewidth values by several hours' measurement at a sample pressure of 1.5 Pa. As for the spectroscopy-determined temperatures, although with a reproducibility better than 10 ppm, we found a systematic deviation of about 800 ppm, which is attributed to "hidden" weak lines overlapped with the selected transition at 787 nm. Our analysis indicates that it is feasible to pursue a DBT measurement toward the 1 ppm precision using cavity ring-down spectroscopy of a CO line at 1.57 mum.

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“…It for instance, constituted 97% of the 144 ppm standard uncertainty published in [29]. The influence of the lineshape model on the spectroscopic determination of the Boltzmann constant has been raised by us and other groups working with O 2 and H 2 O [29,32,[40][41][42][43][44][45]. We recently carried out an extensive lineshape study at relatively high pressure in SPC, in order to enhance collisional effects and to determine the most suitable model for our data [40].…”

Section: The Lineshape Problemmentioning

confidence: 99%

Accurate determination of the Boltzmann constant by Doppler spectroscopy: Towards a new definition of the kelvin

Darquié

Mejri

Sow

et al. 2013

EPJ Web of Conferences

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Abstract. Accurate molecular spectroscopy in the mid-infrared region allows precision measurements of fundamental constants. For instance, measuring the linewidth of an isolated Doppler-broadened absorption line of ammonia around 10 m enables a determination of the Boltzmann constant k B . We report on our latest measurements. By fitting this lineshape to several models which include Dicke narrowing or speeddependent collisional effects, we find that a determination of k B with an uncertainty of a few ppm is reachable. This is comparable to the best current uncertainty obtained using acoustic methods and would make a significant contribution to any new value of k B determined by the CODATA. Furthermore, having multiple independent measurements at these accuracies opens the possibility of defining the kelvin by fixing k B , an exciting prospect considering the upcoming redefinition of the International System of Units.

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Influence of the line-shape model on the spectroscopic determination of the Boltzmann constant

Cited by 50 publications

References 53 publications

Velocity-changing collisions in pure H2 and H2-Ar mixture

Velocity-changing collisions in pure H2 and H2-Ar mixture

Doppler Broadening Thermometry Based on Cavity Ring-Down Spectroscopy

Accurate determination of the Boltzmann constant by Doppler spectroscopy: Towards a new definition of the kelvin

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