Improved measurement results for the Avogadro constant using a 28Si-enriched crystal

Abstract

New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New measurements were then made on these two reconditioned spheres using improved methods and apparatuses. When combined with other recently refined parameter measurements, the Avogadro constant derived from these new results has a value of $N_A=6.02214076(12)\times 10^{23}$ mol${}^{-1}$. The X-ray crystal density method has thus achieved the target relative standard uncertainty of $2.0\times 10^{-8}$ necessary for the realization of the definition of the new kilogram.

postprint, 22 page, 3 figures, 14 tables

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• An accurate determination of the Avogadro constant by counting the atoms in a 28Si crystal
• Determination of the Planck constant using a watt balance with a superconducting magnet system at the National Institute of Standards and Technology
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Cited by in corpus (6)

• CODATA Recommended Values of the Fundamental Physical Constants: 2014
• A more accurate measurement of the ${}^{28}$Si lattice parameter
• The correlation of the $N_A$ measurements by counting ${}^{28}$Si atoms
• 30Si Mole Fraction of a Silicon Material Highly Enriched in 28Si Determined by Instrumental Neutron Activation Analysis
• Density functional theory calculations of the stress of oxidised (110) silicon surfaces
• Isotopic effects in chair graphane