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The '''Boltzmann constant''' (<math>k</math> or <math>k_B</math>) is the physical constant relating [[temperature]] to energy. | The '''Boltzmann constant''' (<math>k</math> or <math>k_B</math>) is the physical constant relating [[temperature]] to energy. | ||
It is named after the Austrian physicist [[Ludwig Eduard Boltzmann]]. | It is named after the Austrian physicist [[Ludwig Eduard Boltzmann]]. | ||
Its experimentally determined value (in SI units, | Its experimentally determined value (in SI units, 2002 [http://physics.nist.gov/cgi-bin/cuu/Value?k#mid CODATA] value) is: | ||
:<math>k_B =1. | :<math>k_B =1.380 6505(24) \times 10^{-23} </math> <math>\left. JK^{-1}\right.</math> | ||
::<math> =8.617 343(15) \times 10^{-5}</math> <math>\left.eV\right.</math> <math>\left.K^{-1}\right.</math> | |||
In units with molecular significance it is close to 1, for example see: [[DL_POLY | DL_POLY units]]. | In units with molecular significance it is close to 1, for example see: [[DL_POLY | DL_POLY units]]. | ||
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Max Planck, [http://nobelprize.org/nobel_prizes/physics/laureates/1918/planck-lecture.html Nobel Lecture, June 2, 1920] | Max Planck, [http://nobelprize.org/nobel_prizes/physics/laureates/1918/planck-lecture.html Nobel Lecture, June 2, 1920] | ||
==Experimental determination of Boltzmann's constant== | ==Experimental determination of Boltzmann's constant== | ||
Boltzmann's constant can be obtained from the ratio of the [[molar gas constant]] to the [[Avogadro constant]] | Boltzmann's constant can be obtained from the ratio of the [[molar gas constant]] to the [[Avogadro constant]]. | ||
The molar gas constant can be obtained via acoustic gas thermometry, and Avogadros constant from either the ''Silicon sphere'', or via the watt balance. | The molar gas constant can be obtained via acoustic gas thermometry, and Avogadros constant from either the ''Silicon sphere'', or via the watt balance. | ||
Recently laser spectroscopy has been used to determine the constant | Recently laser spectroscopy has been used to determine the constant (Refs. 3 and 4). Other techniques include Coulomb blockade thermometry (Refs. 5 and 6). | ||
#[http://dx.doi.org/10.1088/0026-1394/22/3/023 L. Storm "Precision Measurements of the Boltzmann Constant",Metrologia '''22''' pp. 229-234 (1986)] | |||
#[http://dx.doi.org/10.1088/0957-0233/17/10/R01 B Fellmuth, Ch Gaiser and J Fischer "Determination of the Boltzmann constant—status and prospects", Measurement Science and Technology '''17''' pp. R145-R159 (2006)] | |||
#[http://dx.doi.org/10.1103/PhysRevLett.98.250801 C. Daussy, M. Guinet, A. Amy-Klein, K. Djerroud, Y. Hermier, S. Briaudeau, Ch. J. Bordé, and C. Chardonnet "Direct Determination of the Boltzmann Constant by an Optical Method", Physical Review Letters '''98''' 250801 (2007)] | |||
#[http://dx.doi.org/10.1103/PhysRevLett.100.200801 G. Casa, A. Castrillo, G. Galzerano, R. Wehr, A. Merlone, D. Di Serafino, P. Laporta, and L. Gianfrani "Primary Gas Thermometry by Means of Laser-Absorption Spectroscopy: Determination of the Boltzmann Constant", Physical Review Letters '''100''' 200801 (2008)] | |||
#[http://dx.doi.org/10.1103/PhysRevLett.73.2903 J. P. Pekola, K. P. Hirvi, J. P. Kauppinen, and M. A. Paalanen "Thermometry by Arrays of Tunnel Junctions", Physical Review Letters '''73''' pp. 2903-2906 (1994)] | |||
#[http://dx.doi.org/10.1103/PhysRevLett.101.206801 Jukka P. Pekola, Tommy Holmqvist, and Matthias Meschke "Primary Tunnel Junction Thermometry", Physical Review Letters '''101''' 206801 (2008)] | |||
==References== | ==References== | ||
[[Category: Physical constants]] | [[Category: Physical constants]] |