Phys. Rev. Lett. 106, 030801 (2011) [4 pages]Determination of the Avogadro Constant by Counting the Atoms in a 28Si Crystal
See accompanying Physics Synopsis The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA=6.022 140 78(18)×1023 mol-1, is the most accurate input datum for a new definition of the kilogram. © 2011 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.106.030801
DOI:
10.1103/PhysRevLett.106.030801
PACS:
06.20.Jr, 06.30.Dr, 82.80.Ms
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