Application of Thermal Ionization Mass Spectrometry for Measuring Atomic Weight of Dysprosium

Two standard solutions of highly enriched isotopes of 162Dy and 164Dy were prepared from 162Dy and 164Dy in the form of oxides of well-defined purity. Gravimetric synthetic mixtures of two standard solutions were used to calibrate Finnigan MAT-261 Thermal Ionization Mass Spectrometer (TIMS). This instrument were used to determine isotopic abundance ratios on five natural samples of dysprosium to obtain an absolute isotope abundances of 0.056(2)at.% 156Dy, 0.095(2)at.% 158Dy, 2.329(12)at.% 160Dy, 18.889(28)at.% 161Dy, 25.475(24)at.% 162Dy, 24.896(28)at.% 163Dy and 28.260(36)at.% 164Dy. These absolute isotope abundances multiplied by their nuclear mass is equal to Dy atomic weight as 167.2591(9) with an uncertainty given on the basis of 95% confidence limit.