The isotopic contosition of zirconium

Abstract

The isotopic composition of zirconium has been measured. Normalized to 94Zr/ 90Zr = 0.3381, the isotopic ratios are 91Zr/ 90Zr = 0.21799 ± 0.00005, 92Zr/ 90Zr = 0.33338 ± 0.00006, and 96Zr/ 90Zr = 0.05439 ± 0.00007, where the errors correspond to the reproducibility of 14 standard runs. The same isotopic composition has been found in one chondrite, one achondrite and one lunar sample, and one terrestrial standard (granite G2). The absolute mass discrimination has been tested by analysing artificial mixtures of 91Zr- and 96Zr-enriched isotopes. Our preferred isotopic abundances of zirconium are: • 90Zr = 0.51444 +0.085 −0.025 91Zr = 0.11214 +0.008 −0.004 • 92Zr = 0.17150 −0.017 +0.008 94Zr = 0.17393 −0.057 +0.016 • 96Zr = 0.02798 −0.019 +0.008 where the errors are strongly correlated. The corresponding atomic mass of zirconium is 91.224 +0.002 −0.005, in agreement with the accepted value of 91.22.