Fine-structure constant sensitivity of the Th-229 nuclear clock transition.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41093868.
- Also identified by DOI 10.1038/s41467-025-64191-7 and PMC identifier 12528423.
- Licence recorded as CC BY-NC-ND.
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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.