Measurement of the 146Sm Half-Life with Absolute Decay Counting

Samarium-neodymium chronometers are critical tools for nuclear dating and our understanding of Solar-System formation. Prior measurements of the 146Sm half-life range from 68 to 103 million years. This spread causes large uncertainties in the interpretation of planetary samples and Solar System formation models. To address these discrepancies, we have produced a pure and accurately quantified 146Sm sample, embedded it within a gold foil thermal absorber for microcalorimetry, and measured its absolute activity revealing a half-life of 86 ± 0.6 million years. The absolute decay counting technique developed is broadly applicable to further challenges in both fundamental and applied nuclear sciences.