Measurement of the isotopic composition of germanium using GeF_4 produced by direct fluorination and wet chemical procedures

摘要

Two methods are described for the preparation of GeF_4 from Ge and GeO_2 for isotopic measurements: a direct reaction with elemental fluorine and a wet chemical procedure. Germanium isotope amount ratios were obtained using the same measurement procedures and instruments as developed in the framework of the redetermination of the Avogadro constant and taking all significant sources of uncertainty into account. The repeatability of measurements on an individual sample was 5 * 10~(-5) relative. The results on the abundance ratios for different sample materials and preparation techniques agree to within 7 * 10~(-5) relative. All uncertainty statements were made following the ISO/BIPM Guide to the Expression of Uncertainty in Measurements (Geneve, 1993). The calibrated isotope abundance ratios are calculated to be n(~(70)Ge)(~(74)Ge) = 0.5635 (29); n(~(72)Ge)(~(74)Ge) = 0.7519 (38); n(~(73)Ge)(~(74)Ge) = 0.2123 (11); n(~(76)Ge)(~(74)Ge) = 0.2118 (11) resulting in an atomic weight A_r(Ge) = 72.6276 (32). These results are compared to values previously published for the isotopic composition and atomic weight of Ge.