Absolute isotopic composition and atomic weight of dysprosium

Gravimetric synthetic mixtures of highly enriched isotopes of Dy-162 and Dy -164 in the form of oxides of well defined purity were used to calibrate a thermal ionization mass spectrometer. Measurements on five natural samples of dysprosium yielded an absolute isotopic composition of 0.056 (2) at. % D y-156, 0.095(2) at. % Dy-158, 2.329(12) at. % Dy-160, 18.889 (28) at. % Dy- 161, 25.475(24) at. % Dy-162, 24.896(28) at. % Dy-163 and 28.260(36) at. % Dy-164, and the atomic weight of dysprosium as 162.4995(17) with an uncerta inty given on the basis of 95% confidence limit. No isotopic fractionation was found in terrestrial normal dysprosium materials. (C) 2001 Elsevier Sci ence B.V.