HR: 0800h
AN: V51E-0828    [Abstracts]
TI: First measurements on how pressure affects the half-life of 22Na: Comparison to theory and analog to 40K
AU: * Lee, K K
EM: kanani@physics.nmsu.edu
AF: New Mexico State University, Department of Physics MSC 3D, Box 30001, Las Cruces, NM 88003, United States
AU: * Lee, K K
EM: kanani@physics.nmsu.edu
AF: Bayerisches Geoinstitut, Universitat Bayreuth, Bayreuth, 95440, Germany
AU: Nelson, R O
EM: rnelson@lanl.gov
AF: LANSCE, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
AU: Rundberg, R
EM: rundberg@lanl.gov
AF: LANSCE, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
AU: Steinle-Neumann, G
EM: G.Steinle-Neumann@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Universitat Bayreuth, Bayreuth, 95440, Germany
AB: 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.
DE: 1040 Radiogenic isotope geochemistry
DE: 3924 High-pressure behavior
DE: 3994 Instruments and techniques
DE: 4860 Radioactivity and radioisotopes
DE: 8125 Evolution of the Earth (0325)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting