Title

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

Document Type

Conference Proceeding

Publication Date

12-1-2012

Abstract

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. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.

Publication Source (Journal or Book title)

Proceedings of Science

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