ABSOLUTE ISOTOPIC ABUNDANCE RATIOS AND ATOMIC WEIGHT OF A REFERENCE SAMPLE OF STRONTIUM.

Abstract

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 spectrometry. The resulting absolute **8//8Sr/**8**6Sr, **8**7Sr/**8**6Sr, and **8**4Sr/**8**6Sr ratios are 8. 3786 plus or minus 0. 0033, 0. 71034 plus or minus 0. 00026, and 0. 05655 plus or minus 0. 00014 respectively which yields atom percents of: **8**8Sr equals 82. 5845 plus or minus 0. 0066, **8**7Sr equals 7. 0015 plus or minus 0. 0026, **8**6Sr equals 9. 9577 plus or minus 0. 0034, and **8**4Sr equals 0. 5574 plus or minus 0. 0015. The atomic weight calculated from these bundances is 87. 61681 plus or minus 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.