Activity standardization of two enriched 40K solutions for the determination of decay scheme parameters and the half-life

Kossert, Karsten; Amelin, Y.; Arnold, D.; Merle, Renaud; Mougeot, X.; Schmiedel, Michael; Zapata-García, D.

doi:10.1016/j.apradiso.2022.110362

Cited by 9 publications

(19 citation statements)

References 65 publications

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“…Re-evaluation of the 40 K decay scheme. Branching ratios I and total half-life T 1/2 are calculated from our measurement of ρ = I EC 0 /I EC * , evaluation of measured partial EC * and β − halflives [15], and either the measured relative β + /β − feeding [18] or the predicted value of I EC 0 /I β + [12]. The choice only affects the β + branching.…”

Section: Discussionmentioning

confidence: 99%

“…Two of these are partial decay constants for the β − and EC * branches, λ − = 0.4904 ± 0.0019 Ga −1 and λ * = 0.05646 ± 0.00016 Ga −1 (where Ga denotes 10 9 yr), taken from the most recent data evaluation (Sec. 5.2 of [15]). These absolute measurements are independent of EC 0 , though they depend on factors like the precise 40 K content of the source, and the efficiency of the detectors.…”

Section: Quantitymentioning

confidence: 96%

“…1. 40 K decay scheme, with branching ratios and half-life calculated from our determination of I EC 0 /I EC* (this work and [14]) and from literature values for T − (partial half-life of the β − decay) and T * (partial half-life of EC * ) [15] (also shown: transition energy [16], Q EC 0 and Q − [17]). radiation from 40 K electron capture which falls in the expected dark matter signal region [3,4,6].…”

Section: Introductionmentioning

confidence: 95%

“…Aside from the branches mentioned previously, an electron-capture decay directly to the ground state of 40 Ar (EC 0 ) has also been predicted by some [9,13,15,18], ignored or disputed by others [10,11], but never observed. This branch forms a particularly challenging background in rare-event searches as there is no high-energy γ ray from deexcitation that could be used to tag the low-energy radiation from the electron capture.…”

Section: Introductionmentioning

confidence: 95%

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Evidence for ground-state electron capture of K40

Hariasz,

Stukel,

Di Stefano

et al. 2023

Phys. Rev. C

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Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts estimated geological ages spanning billions of years, nuclear structure theory, and subatomic rare-event searches-including those for dark matter and neutrinoless double-beta decay. The decays of this long-lived isotope must be precisely known for its use as a geochronometer, and to account for its presence in low-background experiments. There are several known decay modes for potassium-40, but a predicted electron-capture decay directly to the ground state of argon-40 has never been observed. The existence of this decay mode impacts several fields, while theoretical predictions span an order of magnitude. Here we report on the first, successful observation of this rare decay mode, obtained by the KDK (potassium decay) Collaboration using a novel combination of a low-threshold x-ray detector surrounded by a tonne-scale, high-efficiency γ -ray tagger at Oak Ridge National Laboratory. A blinded analysis reveals a distinctly nonzero ratio of intensities of ground-state electron-captures (I EC 0 ) over excitedstate ones (I EC* ) of I EC 0 /I EC* = 0.0095 stat ± 0.0022 sys ± 0.0010 (68% CL), with the null hypothesis rejected at 4σ [Stukel et al., Phys. Rev. Lett. 131, 052503 (2023)]. In terms of branching ratio, this unambiguous signal yieldsroughly half of the commonly used prediction. This first observation of a third-forbidden unique electron capture improves our understanding of low-energy backgrounds in dark-matter searches and has implications for nuclear-structure calculations. For example, a shell-model based theoretical estimate for the neutrinoless double-beta decay half-life of calcium-48 is increased by a factor of 7 +3 −2 . Our nonzero measurement shifts geochronological ages by up to a percent; implications are illustrated for Earth and solar system chronologies.

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Section: Discussionmentioning

confidence: 99%

Section: Quantitymentioning

confidence: 96%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

See 2 more Smart Citations

Evidence for ground-state electron capture of K40

Hariasz,

Stukel,

Di Stefano

et al. 2023

Phys. Rev. C

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“…We cannot discuss all these examples here and therefore refer to the numerous references listed. A recent and very comprehensive work on the determination of the halflife and other decay parameters of 40 K could be suitable material for interested readers, as it describes many of the previously mentioned difficulties and their solutions [39].…”

Section: Determination Of (Very) Long Half-livesmentioning

confidence: 99%

Liquid scintillation counting: A valuable tool to determine half-lives

2023

Self Cite

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In the past two decades, the radionuclide metrology group at PTB has carried out a number of half-life determinations using liquid scintillation counting. The half-lives, which were often determined in collaboration with other institutions, range from a few ten nanoseconds (e.g., 86 keV level of 233Pa) to several billion years (e.g., 87Rb). This review aims to give an overview of the various half-life determination techniques that have been used and to demonstrate the great potential of liquid scintillation counting as an experimental tool for such measurements.

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In situ beta decay dating by LA-ICP-MS/MS

Zack,

Gilbert

2024

Methods and Applications of Geochronology

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Activity standardization of two enriched 40K solutions for the determination of decay scheme parameters and the half-life

Cited by 9 publications

References 65 publications

Evidence for ground-state electron capture of K40

Evidence for ground-state electron capture of K40

Liquid scintillation counting: A valuable tool to determine half-lives

In situ beta decay dating by LA-ICP-MS/MS

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