科研之友
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摘要
Twenty-first century advances in both the analytical procedures and instrumentation used in geochronology promise age accuracy better than +/- 1 parts per thousand, but realizing this potential requires knowledge of decay constants (lambda) that exceed this level. Given the paucity of improved recent measurements of lambda, the community has experimented with hybrid methodologies utilizing data largely generated during the 1970s. In this article, we perform a systematic review of laboratory decay constant determinations relevant to geochronology (i.e. Rb-87, Sm-147, Lu-176, Th-230, Th-232, U-235, and U-238), focusing on methodological consistency. For radioisotopes for which multiple studies are available, results are combined through a random effects model to yield the best available values and associated uncertainties. Unfortunately, despite its vital role in modern geochronology, only one experimental determination of U-238 decay met our criteria for consideration, significantly limiting the ability to assess its reliability. Thus, utilizing lambda(238) as an anchor for establishing other decay constants (e.g. K-40, Lu-176, and spontaneous U-238 fission) places an unverified result at the core of geochronology. For geochronology to attain its greatest potential, more and better laboratory determinations of decay constants are required, along with a community methodology that permits us to continuously take advantage of new data.
- 出版日期2014-5-19
