Measurement of the Boltzmann constant by the Doppler broadening technique at a 3,8x10-5 accuracy level

Khelifa Djerroud (1) , Cyril Lemarchand (1) , Alexandre Gauguet (1) , Christophe Daussy (1) , Stéphan Briaudeau (2) , Benoît Darquié (1) , Olivier Lopez (1) , Anne Amy-Klein (1) , Christian Chardonnet (1) , Christian J. Bordé (1)

1 LPL - Laboratoire de Physique des Lasers
2 LCM - Laboratoire commun de métrologie LNE-CNAM

In this paper, we describe an experiment performed at the Laboratoire de Physique des Lasers and dedicated to an optical measurement of the Boltzmann constant . With the proposed innovative technique, determining 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 sqrt(kT) and thus to a determination of the Boltzmann constant. The laser source is an ultra-stable CO2 laser with a wavelength . The absorption cell is placed in a thermostat keeping the temperature at 273.15 K within 1.4 mK. We were able to measure with a relative uncertainty as small as 3.8x10-5, which represents an improvement of an order of magnitude for an integration time comparable to our previous measurement published in 2007 [1]

Domaines: Physique Quantique [quant-ph]

Khelifa Djerroud, Cyril Lemarchand, Alexandre Gauguet, Christophe Daussy, Stéphan Briaudeau, et al.. Measurement of the Boltzmann constant by the Doppler broadening technique at a 3,8x10-5 accuracy level. Comptes Rendus. Physique, 2009, 10 (9), pp.883-893. ⟨10.1016/j.crhy.2009.10.020⟩. ⟨hal-00431710⟩