Wetherill, G. W. and Wasserburg, G. J. and Aldrich, L. T. and Tilton, G. R. (1956) Decay Constants of K40 as Determined by the Radiogenic Argon Content of Potassium Minerals. Physical Review, 103 (4). pp. 987-989. ISSN 0031-899X. http://resolver.caltech.edu/CaltechAUTHORS:WETpr56
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It is shown that the potassium-argon age of young minerals depends almost linearly on the decay constant for electron capture in K40 and is very insensitive to the decay constant for beta emission. This fact permits calculation of λe by comparing the concordant uranium-lead age of cogenetic uraninite with A40/K40 ratios found in young samples of mica. It is found that λe=(0.557±0.026)×10^-10 yr^-1. Similar comparisons with older mica samples indicate that satisfactory agreement with the uraninite ages are obtained by use of this value of λe together with λβ=(0.472±0.05)×10^-9 yr^-1. It is concluded that there is no conflict between the decay constants inferred by this geological method and those found by direct counting experiments.
|Additional Information:||©1956 The American Physical Society Received 28 March 1956 Some of these results were obtained in connection with the joint program of mineral age determination of the Department of Terrestrial Magnetism and the Geophysical Laboratory, Carnegie Institution of Washington. Part of the work reported here was supported by the U.S. Atomic Energy Commission and the National Science Foundation. Stable isotopes used in the isotope dilution analyses of potassium, uranium, and lead were obtained on loan from the U.S. Atomic Energy Commission.|
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