M. P. Unterweger, D. D. Hoppes, F. J. Schima, and J. S. Coursey

NIST, PML, Radiation and Biomolecular Physics Division

---

The half lives of many radionuclides have been measured in the Radioactivity Group of NIST. The table below, based on "New and revised half-life measurements results,"^§ by M.P. Unterweger, D.D. Hoppes, and F.J. Schima (1992), is a revised listing of the half lives determined at NIST since 1967. This table supersedes the table presented in NBS Special Publication 626 [D.D. Hoppes and F.J. Schima, ed. (1982), p. 85] as well as that presented in "New and revised half-life measurements results." Included in this table are new values not previously tabulated in either publication. The references are given for these values. Values revised since NBS Special Publication 626 for the half lives of various "short-lived" radionuclides arise from improved impurity analysis, incorporation of additional data from new sources, and reevaluation of old data.

Values in common usage in certificates and reports are available from the National Nuclear Data Center. In case of discrepant data, the NIST value is recommended.