Absolute Isotopic Abundance Ratios and Atomic Weight of a Reference Sample of Strontium

Absolute values have been obtained for the isotopic abundance ratios of a reference sample of strontium using solid sample thermal ionization mass spectrometry. Samples of independently known isotopic composition prepared from chemically pure and nearly isotopically pure separated strontium isotopes were used to calibrate the mass spectrometl),. The resulting absolute IlBSrl B "'Sr. B7Srl~-.Sr. and B4SrlIl6Sr ratios are 8.3786 0.0033. 0.71034 0.00026. and 0.05655 0.00014 respectively which yields atom percents of: BaSr "'" 82.5845 0.0066. B7Sr "'" 7.0015 0.0026, ><fISr = 9.8566 0.0034. and a.1S r = 0.5574 0.0015. The atomic weight calculated from these abundances is 87.61681 0.00012. The indicated uncertainties are overall limits of error based on 95 percent confidence limits for the mean and allowances for the effects of possible systematic error.