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Atomic Weights & Isotopic Compositions
with Relative Atomic Masses


Developers and Contributors:
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset

NIST Physical Measurement Laboratory

The atomic weights are available for elements 1 through 118 and isotopic compositions or abundances are given when appropriate. The atomic weights data were published by M.E. Weiser1 and M. Berglund2 in Atomic Weights of the Elements 2007, and the isotopic compositions data were published by J.K. Böhlke3, J.R. de Laeter4, P. De Bièvre5, H. Hidaka6, H.S. Peiser7, K.J.R. Rosman8, and P.D.P. Taylor9 in Isotopic Compositions of the Elements, 2001. The relative atomic masses of the isotopes data were published by G. Audi10, A.H. Wapstra11, and C. Thibault12 in The 2003 Atomic Mass Evaluation.

These data have been compiled from the above sources for the user's convenience and does not represent a critical evaluation by the NIST Physical Measurement Laboratory.

  1. M. E. Wieser : Department of Physics and Astronomy, University of Calgary, Canada
  2. M. Berglund : European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Belgium
  3. J.K. Böhlke : United States Geological Survey, Reston, Virginia, USA
  4. J.R. de Laeter : Department of Applied Physics, Curtin University of Technology, Australia
  5. P. De Bièvre : Independent Consultant on Metrology in Chemistry, Belgium
  6. H. Hidaka : Department of Earth and Planetary Systems Science, Hiroshima University, Japan
  7. H. S. Peiser : United States Geological Survey, Reston, Virginia, USA
  8. K. J. R. Rosman : Department of Applied Physics, Curtin University of Technology, Australia
  9. P. D. P. Taylor : Institute for Reference Materials and Measurements, European Commission, Belgium
  10. G. Audi : Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Orsay Campus, France
  11. A. H. Wapstra : National Institute of Nuclear Physics and High-Energy Physics, Amsterdam, The Netherlands
  12. C. Thibault : Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Orsay Campus, France
 isotopic compositions link
 link to iupac  link to csnsm

Development of this database was funded in part by NIST's Systems Integration for Manufacturing Applications (SIMA) Program.

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NIST Standard Reference Database 144
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Online: September 1999  -  Last update: July 2010

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