Activity standardization of 22Na

Nähle, O.; Kossert, Karsten; Klein, R.

doi:10.1016/j.apradiso.2008.02.028

Cited by 14 publications

(7 citation statements)

References 22 publications

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“…The value calculated by Mougeot (2018) of 212 ± 0.15 is currently the best estimate of the 40 K EC ground /β + . It is slightly higher than two other recent estimates, our value of 164 or that of Pradler et al (2013) of 150. Given a broad consensus in calculated EC ground /β + over several decades and via a variety of methods, it appears highly likely that it falls in the range 150-212 ( Fig.…”

Section: Comparison With Other Evaluationscontrasting

confidence: 77%

“…(9) using the energy of the decay. Pradler et al (2013) use the Fermi method and data from Bambynek et al (1977) but only perform the calculation for K-shell electrons, resulting in a slightly differently calculated value than we report. Notably, all estimated values are of the same order of magnitude, similar to the ratio 155 reported in Engelkemeir et al (1962) and our calculated value of 164.…”

Section: Comparison With Other Evaluationsmentioning

confidence: 78%

“…2). Pradler et al (2013) and Mougeot (2018) report ratios of 150 and 212 ± 0.15, respectively (uncertainties are reported where they have been estimated). These workers use broadly similar methods to us.…”

Section: Comparison With Other Evaluationsmentioning

confidence: 99%

“…The value of Chen (2017) is not included in the figure as it is an extreme outlier, and the authors do not explain the method they use to reach this value. Our calculated ratios are compared to previous evaluations in the literature (Engelkemeir et al, 1962;Pradler et al, 2013;Mougeot, 2018). Uncertainties in these values are either intractable or, in the case of Mougeot (2018), too small to plot.…”

Section: Comparison With 22 Namentioning

confidence: 99%

“…Unlike 40 K, there are numerous measurements of the electron capture to positron ratio for decay to the excited state of 22 Ne (Fig. 4; Kreger, 1954;Vatai et al, 1968;Williams, 1964;McCann and Smith, 1969;MacMahon and Baerg, 1976;Bosch et al, 1977;Baerg, 1983;Schmidt-Ott et al, 1984;Sýkora and Povinec, 1986;Kunze et al, 1990;Nähle et al, 2008). Measurement of (EC/β + )* for 22 Na is accomplished by measurement of both of the gammas (which come from both the EC* and the β + * ) and the x-rays (which only come from the EC branch).…”

Section: Comparison With 22 Namentioning

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: Comparison With Other Evaluationscontrasting

confidence: 77%