@article{13474,
  author = {Kjeld Beeks and Georgy Kazakov and Fabian Schaden and Ira Morawetz and Luca de Col and Thomas Riebner and Michael Bartokos and Tomas Sikorsky and Thorsten Schumm and Chuankun Zhang and Tian Ooi and Jacob Higgins and Jack Doyle and Jun Ye and Marianna Safronova},
  title = {Fine-structure constant sensitivity of the Th-229 nuclear clock transition},
  abstract = {<p>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<br>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<br>models. Using a semi-classical prolate-spheroid model, we quantify the transition frequency’s sensitivity to fine-structure constant variations as<br>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<br>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 ΔQ0/Q0 underlines the need for improved modeling and measurement of additional nuclear parameters. We explicitly assess the octupole contribution to α-sensitivity.</p>},
  year = {2025},
  journal = {Nature Communications},
  volume = {16},
  pages = {9147},
  month = {2025-09},
  url = {https://www.nature.com/articles/s41467-025-64191-7},
  doi = {10.1038/s41467-025-64191-7},
}