IUGS-IUPAC recommendation on the half-lives of 147Sm and 146Sm

The IUPAC-IUGS joint Task Group “Isotopes in Geosciences” recommends a value of (106.25 ± 0.38) Ga for the half-life of 147Sm, and a corresponding decay constant λ147 = (6.524 ± 0.024) × 10-12 a-1, both with a coverage factor k = 2. For the extinct radionuclide 146Sm two very different half-lives are used in the scientific community (c. 68 and 103 Ma), to such a degree that no consensus value can be endorsed at present by the Task Group. Pending dedicated re-investigations it is recommended that papers using the 146Sm decay to quantify the cosmo/geological evolution of (extra)terrestrial samples perform a twin set of calculations using both proposed half-lives.