Statistics – Computation
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.v51e0828l&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #V51E-0828
Statistics
Computation
1040 Radiogenic Isotope Geochemistry, 3924 High-Pressure Behavior, 3994 Instruments And Techniques, 4860 Radioactivity And Radioisotopes, 8125 Evolution Of The Earth (0325)
Scientific paper
Radioactive decay plays a central role in planetary sciences as appropriate decay schemes are used to date geological and astronomical processes and radioactivity provides an important source of heat in planetary bodies, both in their early history during accretion and differentiation and also over geological times. The most important isotopes that currently heat the Earth are 40K, 232Th, 235U and 238U. As radioactive decay is a nuclear process it is considered to be insensitive to external factors such as pressure or chemical environment. This has been shown to be true for α, β+ and β- processes, however, electron capture decay is dependent on the electron charge density at the nucleus of a compound, which is sensitive to the external environment. Using high-resolution Ge gamma-ray detectors to make relative measurements with 137Cs and the positron decay of 22Na, we measure how pressure affects the half-life of 22Na due to electron-capture decay. Our systematics look favorable for observing this small effect. We will compare our preliminary measurements with complementary ab-initio all-electron computations using the linearized augmented plane wave method (LAPW). Using 22Na as an analog for 40K, our results suggest that the pressure effect for 40K, combined with the opposing effects of high temperatures, will have little, discernible effect on the heat production in the deep Earth as our predicted changes are smaller than the uncertainties in the total decay constant for 40K. This work was supported in part by the Carnegie/DOE Alliance Center (CDAC), through the Stewardship Science Academic Alliances Program of the U.S. Department of Energy. The LANSCE facility is operated, and portions of this work were performed, by Los Alamos National Security, LLC, funded by the U.S. Department of Energy under Contract No. DE-AC52- 06NA25396.
Lee Kimyeong
Nelson Ronald O.
Rundberg R.
Steinle-Neumann Gerd
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