New Silicon Crystals for a Redefined Kilogram and Mole: Isotopic Composition of the First Two Crystals

摘要

The isotopic compositions (molar mass, M) of the first and new silicon crystals highly enriched in 28 Si (> 99.99 %) used for the determination of the Avogadro constant were measured using a high resolution multicollector ICP mass spectrometer and applying a modified isotope dilution mass spectrometry technique. Relative uncertainties u_(rel) (M) <; 1 × 10~(-9) were obtained: a reduction by almost three orders of magnitude in ten years. This study compares the homogeneities in M(Si) of the first "AVO28" crystal and the first crystal (Si28-23Pr11) of the "Kilogram-2" project.