Determination of Isotopic Abundance of Europium by Calibrating Mass Spectrometry

Nine synthetic mixtures prepared from two highly enriched isotopes of europium in the form of well-defined pure sesquioxide served to calibrate the mass spectrometer,the absolute isotopic abundance ratios of europium in 8 samples from various origins are de-termined by calibrating mass spectrometer,vielding absolute isotopic composition of 47.810 (42)at. %151 Eu and 52. 190 (42)at. %,153,Eu. The atomic weight of europium is 151.9644(9) with error giver as 2σ. The atomic weight is accepted as a new international standard value.