IUGS–IUPAC recommendations and status reports on the half-lives of ⁸⁷Rb, ¹⁴⁶Sm, ¹⁴⁷Sm, ²³⁴U, ²³⁵U, and ²³⁸U (IUPAC Technical Report)

Abstract The IUPAC–IUGS joint Task Group “Isotopes in Geosciences” (TGIG) has evaluated the published literature on half-lives of six long-lived, geologically relevant radioactive nuclides. Where conflicting estimates are present, it is necessary to first identify any systematic bias accordance with metrological traceability and exclude biased from further consideration. TGIG recommends three robust half-life estimates: 49.61 ± 0.16 Ga for 87 Rb, corresponding a decay constant λ ( Rb) = (1.3972 0.0045) × 10 −11 −1 ; 106.25 0.38 147 Sm, Sm) (6.524 0.024) −12 4.4683 0.0096 238 U, i.e . U) (1.55125 0.00333) −10 All cited uncertainties have coverage factor k 2. For other radionuclides Sm no unambiguous consensus value can be endorsed at present by TGIG, which limits its evaluation status report highlighting unaccounted-for potential sources bias. improved repeatability mass spectrometric measurements revealed effects that had been dismissed as subordinate past. These issues only resolved future dedicated investigations.