Abstract
Absolute values have been obtained for the isotopic abundance ratios of a reference sample of nickel (Standard Reference Material 986), using thermal ionization mass spectrometry. Samples of known isotopic composition, prepared from nearly isotopically pure separated nickel isotopes, were used to calibrate the mass spectrometers. The resulting absolute isotopic ratios are: (58)Ni/(60)Ni=2.596061±0.000728, (61)Ni/(60)Ni=0.043469±0.000015,(62)Ni/(60)Ni=0.138600±0.000045, and (64)Ni/(60)Ni=0.035295±0.000024, which yield atom percents of (58)Ni=68.076886 ±0.005919, (60)Ni = 26.223146±0.005144,(61)Ni=1.139894±0.000433, (62)Ni =3.634528±0.001142, and (64)Ni =0.925546±0.000599. The atomic weight calculated from this isotopic composition is 58.693353 ±0.000147. The indicated uncertainties are overall limits of error based on two standard deviations of the mean and allowances for the effects of known sources of possible systematic error.