First direct determination of the Boltzmann constant by an optical method

Christophe Daussy (1) , Mickael Guinet (1) , Anne Amy-Klein (1) , Khelifa Djerroud (1) , Yves Hermier (2) , Stéphan Briaudeau (2) , Christian J. Bordé (1) , Christian Chardonnet (1)

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

We have recorded the Doppler profile of a well-isolated rovibrational line in the ν2 band of 14NH3. 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, kB, by laser spectroscopy. A relative uncertainty of 2x10-4 has been obtained. The present determination should be significantly improved in the near future and contribute to a new definition of the kelvin.

Mots clés: Boltzmann constant; Doppler width; molecular spectroscopy

Domaines: Physique Quantique [quant-ph]

Christophe Daussy, Mickael Guinet, Anne Amy-Klein, Khelifa Djerroud, Yves Hermier, et al.. First direct determination of the Boltzmann constant by an optical method. Physical Review Letters, 2007, 98 (25), pp.250801. ⟨10.1103/PhysRevLett.98.250801⟩. ⟨hal-00126269⟩