%0 Journal Article
%T First direct determination of the Boltzmann constant by an optical method
%A Christophe Daussy
%A Mickael Guinet
%A Anne Amy-Klein
%A Khelifa Djerroud
%A Yves Hermier
%A Stephan Briaudeau
%A Christian J. Bord¨¦
%A Christian Chardonnet
%J Physics
%D 2007
%I arXiv
%R 10.1103/PhysRevLett.98.250801
%X We have recorded the Doppler profile of a well-isolated rovibrational line in the \nu2 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.
%U http://arxiv.org/abs/quant-ph/0701176v1