@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>State-resolved laser spectroscopy at the 10−12&nbsp;precision level recently reported in&nbsp;arXiv:<a data-arxiv-id="2406.18719" href="https://arxiv.org/abs/2406.18719">2406.18719</a>&nbsp;determined the fractional change in nuclear quadrupole moment between the ground and isomeric state of&nbsp;229Th,&nbsp;ΔQ0/Q0=1.791(2) %. Assuming a prolate spheroid nucleus, this allows to quantify the sensitivity of the nuclear transition frequency to variations of the fine-structure constant&nbsp;α&nbsp;to&nbsp;K=5900(2300), with the uncertainty dominated by the experimentally measured charge radius difference&nbsp;Δ⟨r2⟩&nbsp;between the ground and isomeric state. This result indicates a three orders of magnitude enhancement over atomic clock schemes based on electron shell transitions. We find that&nbsp;ΔQ0&nbsp;is highly sensitive to tiny changes in the nuclear volume, thus the constant volume approximation cannot be used to accurately relate changes in&nbsp;⟨r2⟩&nbsp;and&nbsp;Q0. The difference between the experimental and estimated values in&nbsp;ΔQ0/Q0&nbsp;raises a further question on the octupole contribution to the alpha-sensitivity.</p>},
  year = {2024},
  journal = {Submitted},
  url = {https://arxiv.org/abs/2407.17300},
}