Prediction of nuclear clock transition frequency difference between 229Th3+ and 229Th4+ via ab initio self-consistent field theory
摘要
The 229Th isotope is a promising candidate for nuclear clocks. However, the clock transition varies due to the electron-induced nuclear frequency shift. To achieve the accuracy required for developing a nuclear clock, this effect must be precisely determined. In this work, we employed a non-perturbative multi-configuration Dirac-Hartree-Fock (MCDHF) method, in contrast to the perturbation theory used previously, to resolve the electron-induced field shift effect. As a more internally consistent ab initio method, this calculation accounts for subtle differences in the nuclear potential while considering the 229Th isotope in both its ground and isomeric states. Consequently, the nuclear clock transition frequency difference between 229Th3+ and 229Th4+ was determined to be −639 MHz with computational convergency down to 1 MHz. Given recently measured transition frequency of 229Th4+ in 229Th-doped CaF2 [Nature 633, 63 (2024)], here the transition frequency of isolated 229Th3+ is predicted to be