Ionization through Nuclear Electron Capture and Internal Conversion

Emery, G.T.

doi:10.1016/b978-0-12-196901-1.50010-8

Cited by 3 publications

(10 citation statements)

References 92 publications

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“…3. β + decay from the ground state of 40 K to the ground state of 40 Ar (Engelkemeir et al, 1962), this is a very small component of the total decay rate and has been verified by direct measurement of the β + emission.…”

Section: Historical Overviewmentioning

confidence: 62%

“…In their paper reporting the measurement of β + /β − , Engelkemeir et al (1962), through private correspondence with Brosi and Kettle, proposed that an electron capture mode that goes directly to ground-state 40 Ar also exists, with an electron capture to positron ratio of 155. This decay mode is hereafter denoted EC ground .…”

Section: Historical Overviewmentioning

confidence: 99%

“…Therefore, the EC* branch, with an energy difference of only 44 keV, cannot be the complement to the β + decay, and the EC ground must exist to provide the β + complement. The experimental observation of the β + decay mode comes from a single measurement by Engelkemeir et al (1962). We rely on this measurement to make our argument for the existence the EC ground .…”

Section: Why There Must Be An Ec Ground Decay Modementioning

confidence: 99%

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Production of 40Ar by an overlooked mode of 40K decay with implications for K-Ar geochronology

et al. 2020

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Abstract. The decay of 40K to the stable isotopes 40Ca and 40Ar is used as a measure of time for both the K-Ca and K-Ar geochronometers, the latter of which is most generally utilized by the variant 40Ar∕39Ar system. The increasing precision of geochronology has forced practitioners to deal with the systematic uncertainties rooted in all radioisotope dating methods. A major component of these systematic uncertainties for the K-Ar and 40Ar∕39Ar techniques is imprecisely determined decay constants and an incomplete knowledge of the decay scheme of 40K. Recent geochronology studies question whether 40K can decay to 40Ar via an electron capture directly to ground state (ECground), citing the lack of experimental verification as reasoning for its omission. In this study, we (1) provide a theoretical argument in favor of the presence of this decay mode and (2) evaluate the magnitude of this decay mode by calculating the electron capture to positron ratio (ECground/β+) and comparing calculated ratios to previously published calculations, which yield ECground/β+ between 150–212. We provide support for this calculation through comparison of the experimentally verified ECground/β+ ratio of 22Na with our calculation using the theory of β decay. When combined with measured values of β+ and β− decay rates, the best estimate for the calculated ECground/β+ for 40K yields a partial decay constant for 40K direct to ground-state 40Ar of 11.6±1.5×10-13 a−1 (2σ). We calculate a partial decay constant of 40K to 40Ar of 0.592±0.014×10-10 a−1 and a total decay constant of 5.475±0.107×10-10 a−1 (2σ), and we conclude that although omission of this decay mode can be significant for K-Ar dating, it is minor for 40Ar∕39Ar geochronology and is therefore unlikely to have significantly biased published measurements.

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Section: Historical Overviewmentioning

confidence: 62%

Section: Historical Overviewmentioning

confidence: 99%

Section: Why There Must Be An Ec Ground Decay Modementioning

confidence: 99%

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Production of 40Ar by an overlooked mode of 40K decay with implications for K-Ar geochronology

et al. 2020

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“…where x is the shell, n x is the relative occupation number, C x contains the dependence of electron capture rates on nuclear 135 structure giving the forbiddenness classification, similar to the shape factor in decay (Emery, 1975), f x is the integrated fermi function in β decay, f β+ is the integrated positron spectrum, and C(W) is the theoretical shape factor for allowed or forbidden transitions. A review of shape factors for 40 K transitions is provided by Cresswell et al (2018Cresswell et al ( , 2019.…”

Section: Theory and Calculation Of Ec Ground /β +mentioning

confidence: 99%

“…CC BY 4.0 License. the initial and final states, as positron decay will have a greater possibility of occurring in decays with a greater mass differences between initial and final states (Emery, 1975). Leutz et al (1965).…”

Section: Comparison With 22 Namentioning

confidence: 99%

Percent-level production of 40Ar by an overlooked mode of 40K decay

Carter¹,

Ickert²,

Mark³

et al. 2020

Preprint

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Abstract. The decay of 40K to the stable isotopes 40Ca and 40Ar is used as a measure of time for both the K-Ca and K-Ar geochronometers, the latter of which is most generally utilized by the variant 40Ar/39Ar system. The increasing precision of geochronology has forced practitioners to deal with the systematic uncertainties rooted in all radioisotope dating methods. A major component of these systematic uncertainties for the K-Ar and 40Ar/39Ar techniques is imprecisely determined decay constants and an incomplete knowledge of the decay scheme of 40K. Recent studies question whether 40K can decay to 40Ar via an electron capture directly to ground state (ECground), citing the lack of experimental verification as reasoning for its omission. In this study, we (1) provide a theoretical argument in favour of the presence of this decay mode, and (2) evaluate the magnitude of this decay mode by calculating the electron capture to positron ratio (ECground&#8201;/&#8201;&#946;+) and after combining it with other estimates, provide a best estimate of 175&#8201;&#177;&#8201;65 (2&#963;). We provide support for this calculation through comparison of the experimentally verified ECground&#8201;/&#8201;&#946;+ ratio of 22Na with our calculation using the theory of &#946; decay.When combined with measured values of &#946;+ and &#946;- decay rates, this yields a partial decay constant for 40K direct to ground state 40Ar of 9.6&#8201;&#177;&#8201;3.8&#8201;&#215;&#8201;10&#8722;13&#8201;a&#8722;1 (2&#963;). We calculate a partial decay constant of 40K to 40Ar of 0.590&#8201;&#177;&#8201;0.014&#8201;&#215;&#8201;10&#8722;10&#8201;a&#8722;1, total decay constant of 5.473&#8201;&#177;&#8201;0.107&#8201;&#215;&#8201;10&#8722;10&#8201;a&#8722;1 (2&#963;), and conclude that although omission of this decay mode can be significant for K-Ar dating, it is minor for 40Ar/39Ar geochronology and is therefore unlikely to have significantly biased published measurements.

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Study of theK α satellites and hypersatellites in the x-ray and Auger spectra of neon

1986

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Ionization through Nuclear Electron Capture and Internal Conversion

Cited by 3 publications

References 92 publications

Production of <sup>40</sup>Ar by an overlooked mode of <sup>40</sup>K decay with implications for K-Ar geochronology

Production of <sup>40</sup>Ar by an overlooked mode of <sup>40</sup>K decay with implications for K-Ar geochronology

Percent-level production of <sup>40</sup>Ar by an overlooked mode of <sup>40</sup>K decay

Study of theK α satellites and hypersatellites in the x-ray and Auger spectra of neon

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Ionization through Nuclear Electron Capture and Internal Conversion

Cited by 3 publications

References 92 publications

Production of &lt;sup&gt;40&lt;/sup&gt;Ar by an overlooked mode of &lt;sup&gt;40&lt;/sup&gt;K decay with implications for K-Ar geochronology

Production of &lt;sup&gt;40&lt;/sup&gt;Ar by an overlooked mode of &lt;sup&gt;40&lt;/sup&gt;K decay with implications for K-Ar geochronology

Percent-level production of &lt;sup&gt;40&lt;/sup&gt;Ar by an overlooked mode of &lt;sup&gt;40&lt;/sup&gt;K decay

Study of theK α satellites and hypersatellites in the x-ray and Auger spectra of neon

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Production of <sup>40</sup>Ar by an overlooked mode of <sup>40</sup>K decay with implications for K-Ar geochronology

Production of <sup>40</sup>Ar by an overlooked mode of <sup>40</sup>K decay with implications for K-Ar geochronology

Percent-level production of <sup>40</sup>Ar by an overlooked mode of <sup>40</sup>K decay