Article

Direct determination of the Boltzmann constant by an optical method

Laboratoire de Physique des Lasers, UMR CNRS 7538, Institut Galilée, Université Paris 13, 99, avenue J.-B. Clément, 93430 Villetaneuse, France.
Physical Review Letters (Impact Factor: 7.73). 07/2007; 98(25):250801. DOI: 10.1103/PhysRevLett.98.250801
Source: PubMed

ABSTRACT We have recorded the Doppler profile of a well-isolated rovibrational line in the nu(2) band of (14)NH(3). Ammonia gas was placed in an absorption cell thermalized by a water-ice bath. By extrapolating to zero pressure, we have deduced the Doppler width which gives a first measurement of the Boltzmann constant k(B) by laser spectroscopy. A relative uncertainty of 2 x 10(-4) has been obtained. The present determination should be significantly improved in the near future and contribute to a new definition of the kelvin.

Full-text

Available from: M. Guinet, May 13, 2015
1 Follower
 · 
154 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: As is always accompanying temperature in physics fundamental principles, Boltzmann constant k B can be used to verify the accuracy of a thermometer. This paper presents a photoluminescent method to measure k B via temperature dependent fluorescence of phosphors. Diagram of a phosphor’s energy levels was simplified to illustrate the principle of measurement. The relationship between k B and h*c (Planck constant h multiplying light speed in vacuum c) was experimentally derived. Finally, the determined k B was 1.38065 × 10−23 J/K. The determination could give a value of (1.38±0.1) × 10−23 J/K even when the in-use spectrometer was with a poor resolution as about 2 nm. At the end, optimization of measuring conditions for the determination process was suggested.
    03/2013; 7(1):64-68. DOI:10.1007/s12200-013-0369-z
  • [Show abstract] [Hide abstract]
    ABSTRACT: A cavity ring-down spectrometer is built for trace gas detection using telecom distributed feedback (DFB) diode lasers. The longitudinal modes of the ring-down cavity are used as frequency markers without active-locking either the laser or the high-finesse cavity. A control scheme is applied to scan the DFB laser frequency, matching the cavity modes one by one in sequence and resulting in a correct index at each recorded spectral data point, which allows us to calibrate the spectrum with a relative frequency precision of 0.06 MHz. Besides the frequency precision of the spectrometer, a sensitivity (noise-equivalent absorption) of 4×10−11 cm−1 Hz−1/2 has also been demonstrated. A minimum detectable absorption coefficient of 5×10−12 cm−1 has been obtained by averaging about 100 spectra recorded in 2 h. The quantitative accuracy is tested by measuring the CO2 concentrations in N2 samples prepared by the gravimetric method, and the relative deviation is less than 0.3%. The trace detection capability is demonstrated by detecting CO2 of ppbv-level concentrations in a high-purity nitrogen gas sample. Simple structure, high sensitivity, and good accuracy make the instrument very suitable for quantitative trace gas analysis.
    Applied Optics 11/2014; 53(32). DOI:10.1364/AO.53.007716 · 1.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To provide new determinations of the Boltzmann constant, k, which has been asked for by the International Committee for Weights and Measures concerning preparative steps towards new definitions of the kilogram, the ampere, the kelvin and the mole, an iMERAPlus joint research project has coordinated the European activities in this field. In this major European research project the Boltzmann constant has been determined by various methods to support the new definition of the kelvin. The final results of the project are reviewed in this paper. Determinations of the Boltzmann constant k were achieved within the project by all three envisaged methods: acoustic gas thermometry, Doppler broadening technique, and dielectric constant gas thermometry. The results were exploited by the interdisciplinary Committee on Data for Science and Technology (CODATA) in their 2010 adjustment of recommended values for fundamental constants. As a result, the CODATA group recommended a value for k with a relative standard uncertainty about a factor of two smaller than the previous u(k)/k of 1.7×10−6
    Temperature - its measurement and control in science and industry, Los Angeles, California, USA; 03/2012