Fine-structure constant sensitivity of the Th-229 nuclear clock transition

Nuclear laser spectroscopy at the 10<sup>-12</sup> precision level (Nature 633.8028 (2024): 63-70) determined the fractional change in the nuclear quadrupole moment of <sup>229</sup>Th upon excitation, ΔQ<sub>0</sub>/Q<sub>0</sub> = 1.791(2)%. Such high-accuracy nuclear parameters enable stringent tests and refinement of <sup>229</sup>Th nuclear models. Using a semi-classical prolate-spheroid model, we quantify the transition frequency's sensitivity to fine-structure constant variations as K = 5900(2300), with uncertainty dominated by the measured charge-radius change Δ〈r<sup>2</sup>〉. This supports the predicted higher α-sensitivity of nuclear clocks over atomic clocks, important for new-physics searches. We find ΔQ<sub>0</sub> strongly dependent on nuclear volume, challenging the constant-volume approximation. The deviation between measured and predicted ΔQ<sub>0</sub>/Q<sub>0</sub> underlines the need for improved modeling and measurement of additional nuclear parameters. We explicitly assess the octupole contribution to α-sensitivity.

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Publication Details

Journal
Nature Communications
Published
2025-10-15
DOI
https://doi.org/10.1038/s41467-025-64191-7
Citations
10
Primary Topic
Advanced Frequency and Time Standards
Type
article
Field-Weighted Citation Impact
12.47

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article

Fine-structure constant sensitivity of the Th-229 nuclear clock transition

Thorsten Schumm, Georgy A. Kazakov, Fabian Schaden, Jacob S. Higgins et al.
10 citations
Nature Communications
Advanced Frequency and Time Standards
12.47
article

Fine-structure constant sensitivity of the Th-229 nuclear clock transition

Thorsten Schumm, Georgy A. Kazakov, Fabian Schaden, Jacob S. Higgins, Michael Bartokos, Tomáš Šikorský, Chuankun Zhang, M. S. Safronova, Kjeld Beeks, Tian Ooi, L. Toscani De Col, I. Morawetz, Jun Ye, Jack F. Doyle, Thomas Riebner
article en
10 citations

Abstract

Nuclear laser spectroscopy at the 10<sup>-12</sup> precision level (Nature 633.8028 (2024): 63-70) determined the fractional change in the nuclear quadrupole moment of <sup>229</sup>Th upon excitation, ΔQ<sub>0</sub>/Q<sub>0</sub> = 1.791(2)%. Such high-accuracy nuclear parameters enable stringent tests and refinement of <sup>229</sup>Th nuclear models. Using a semi-classical prolate-spheroid model, we quantify the transition frequency's sensitivity to fine-structure constant variations as K = 5900(2300), with uncertainty dominated by the measured charge-radius change Δ〈r<sup>2</sup>〉. This supports the predicted higher α-sensitivity of nuclear clocks over atomic clocks, important for new-physics searches. We find ΔQ<sub>0</sub> strongly dependent on nuclear volume, challenging the constant-volume approximation. The deviation between measured and predicted ΔQ<sub>0</sub>/Q<sub>0</sub> underlines the need for improved modeling and measurement of additional nuclear parameters. We explicitly assess the octupole contribution to α-sensitivity.

Nature CommunicationsVol. 16(1)
Joint Institute for Laboratory Astrophysics (US), Charles University (CZ), Vienna Center for Quantum Science and Technology (AT), École Polytechnique Fédérale de Lausanne (CH), University of Delaware (US)
European Commission, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Austrian Science Fund, HORIZON EUROPE Framework Programme
Openalex Percentile: Top 1%
Advanced Frequency and Time Standards
12.47
DOIOpen Access PDFOpenAlex
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