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MS: Massenspektrometrie

MS I: HV I

MS I.1: Hauptvortrag

Montag, 3. April 2000, 14:00–14:30, HS VII

No-dqAbsoluteNo-dqIsotopenmessungen an Silicium-Einkristallen für eine neue Definition des Kilogramms — •Paul de Bievre — Institute for Reference Materials and -Measurements, European Commission - JRC, B-2440 Geel (Belgium)

Over a period of more than fifteen years, IRMM (Geel), PTB (Braunschweig), IMGC (Torino) and NRLM (Tsukuba) have been cooperating on improving our knowledge of the Avogadro constant by performing measurements - with the smallest possible complete uncertainty - of the isotopic composition and molar mass of Si in Si single crystals, of the density of these crystals and of the lattice constant in these crystals. Combined, they yield a value for the Avogadro constant.

The isotopic measurements and their calibration No-dqcalibrationNo-dqas well as the No-dqAvogadro II amount comparator No-dqwith which these isotopic measurements are performed, are described. It is shown how the smallest complete uncertainties ever achieved in measurements of isotope abundance ratios, are obtained and how the results can be combined with density and lattice parameter values to yield the Avogadro constant.

Some consequences for the development of No-dqMetrology in ChemistryNo-dqare discussed.