P Becker et al 2007 Metrologia 44 1 doi:10.1088/0026-1394/44/1/001
P Becker1, P De Bièvre2, K Fujii3, M Glaeser1,6, B Inglis4, H Luebbig1 and G Mana5
Show affiliationsThe definitions of some units of the Système International are likely to be revised as early as 2011 by basing them on fixed values of fundamental constants of nature, provided experimental realizations are demonstrated with sufficiently small uncertainties. As regards the kilogram, experiments aiming at linking it to the Planck constant and the atomic mass constant are under way in several laboratories. The other units likely to be redefined are the ampere, the kelvin and the mole. We discuss the advantages and disadvantages of different alternatives for revised definitions of the kilogram and the mole. From physical considerations, metrological consequences and ease of understanding, a definition of the kilogram based on the mass of a particle, such as an atom or the electron, is favoured. One of the proposed definitions fixes the value of the Planck constant through the Compton frequency of a material, though unphysical, particle. Finally, a redefinition of the mole, the counting unit of the amount-of-substance, is proposed which fixes the Avogadro constant as a dimensionless number.
Issue 1 (February 2007)
Received 15 September 2006
Published 11 December 2006
P Becker et al 2007 Metrologia 44 1
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