Title: Determination of the Avogadro Constant: A Contribution to the New Definition of Mass
Authors: BUSCH I.VALKIERS StafBECKER P.
Citation: Proceedings of the 13th International Metrology Congress: Transverse Disciplines in Metrology, ISBN: 9781848210486 p. 135-146
Publisher: John Wiley & Sons Inc
Publication Year: 2009
JRC N°: JRC49263
URI: http://eu.wiley.com/WileyCDA/WileyTitle/productCd-1848210485.html
http://publications.jrc.ec.europa.eu/repository/handle/JRC49263
Type: Contributions to Conferences
Abstract: An improved attempt of several national metrology institutes to replace the present definition of the kilogram with the mass of a certain number of 12C atoms is described. This requires the determination of the Avogadro constant, NA, via the silicon route with a relative uncertainty better than 2×10-8. Previously, the limiting factor is the measurement of the average molar mass. Consequently, a world-wide collaboration has been set up, to produce, approximately, 5 kg of 28Si single-crystal with an enrichment factor greater than 99.985% to be used for an improved determination of NA. The first successful tests of all technological steps (enrichment of SiF4, purification and synthesis of silane, deposition of polycrystalline 28Si, single crystal growth) for the production of high-purity 28Si are reported.
JRC Institute:Institute for Reference Materials and Measurements

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