Direct determination of the half-life of 187Re

Abstract We have determined the beta-decay half-life of 187 Re to be (4.23 ± 0.13) · 10 10 y, stated at the 95% confidence level. The method consisted of separating the daughter 187 Os atoms from large sources of initially osmium-free rhenium. Yields were measured by the isotope dilution method using inductively coupled plasma mass spectrometry. Precision was gained through the use of two independent spike isotopes on each of five separate, large sources of rhenium. Because of the present lack of knowledge of other unrelated but equally important parameters, our value does not substantially narrow the range of uncertainty for the duration of galactic nucleosynthesis. However, the use of our half-life value to reinterpret the measurements of others on iron meteorites and chondrites suggests that iron meteorites might be 380 ± 160 million years younger than chondrites. Our half-life result may therefore have more profound implications for solar-system chronology than for galactic nucleosynthesis.