Shorter half-life of p-process ¹⁴⁶Sm measured and ¹⁴⁶Sm/¹⁴²Nd chronology of the Solar System

The short-lived nuclide ¹⁴⁶Sm, synthesized in stellar events by the p-process and now extinct in the Solar System, serves as both an astrophysical and geochemical chronometer through measurements of isotopic anomalies of its α-decay daughter ¹⁴²Nd. Using artificially produced ¹⁴⁶Sm via ¹⁴⁷Sm(γ,n), ¹⁴⁷Sm(n, 2n) and ¹⁴⁷Sm(p,nε) reactions, we performed a new measurement of the ¹⁴⁶Sm half-life by measuring the ¹⁴⁶Sm/ ¹⁴⁷Sm alpha activity with a Si surface barrier detector and the ¹⁴⁶Sm/¹⁴⁷Sm atom ratio with accelerator mass spectrometry (AMS). Our result, t¹₁⁴_/ ⁶₂ = 68 ± 7 (1σ) million years (My), is significantly shorter than the adopted value (103 ± 5 My). The shorter ¹⁴⁶Sm half-life value implies a higher initial Solar System ratio, (¹⁴⁶Sm/¹⁴⁴Sm)₀ = 0.0094 ± 0.0005 (2σ), than the recently derived value 0.0085 ± 0.0007(2σ). The time interval between isolation of the Solar Nebula from the interstellar medium and formation of the first solids, is reduced by a factor of ∼2.5 to 20 from previous estimates. Early planetary mantle differentiation processes on Earth, the Moon and Mars dated by ¹⁴⁶Sm-¹⁴²Nd converge to a shorter time span, due to the combined effect of the new ¹⁴⁶Sm half-life and (¹⁴⁶Sm/¹⁴⁴Sm)₀ values.