SKM 2021 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 9: Instrumentation and Methods

KFM 9.2: Vortrag

Mittwoch, 29. September 2021, 12:15–12:30, H1

Silicon Highly Enriched in 28Si: Probing Artificial Crystals for the Dissemination of the Mole and Kilogram — •Axel Pramann and Olaf Rienitz — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany

The revision of the SI units mole and kilogram has been enabled by the redetermination of the Avogadro constant with the lowest uncertainty by the the X-ray-crystal-density (XRCD) method *counting* silicon atoms in single-crystalline silicon spheres (1) and the complementary realization of the Planck constant using a Kibble balance (2). For the XRCD method applied by PTB, a few unique silicon single crystals highly enriched in 28Si has been produced and characterized. Using a high-resolution MC-ICP mass spectrometer and a tailored analytical methodology in a key experiment, the isotopic composition (the molar mass M) of these crystals has been determined with associated uncertainties of urel(M) < 1 x 10-9, which is unique in chemistry up to now. After developing and improving this method during the last decade, the uncertainties u(M) were reduced by almost three orders of magnitude. The way how to disseminate the amount of substance and mass after the revision of the SI is outlined (1, 3).

(1) K. Fujii et al., Metrologia, 53, A19 (2016). (2) I. A. Robinson, S. Schlamminger, Metrologia, 53, A46 (2016). (3) B. Guettler, O. Rienitz, A. Pramann, Annalen der Physik, 1800292 (2018).