Laser spectroscopy of triply charged 229Th isomer for a nuclear clock

• 成果类型: Article
• 署名作者: Yamaguchi, Atsushi; Shigekawa, Yudai; Haba, Hiromitsu; Kikunaga, Hidetoshi; Shirasaki, Kenji; Wada, Michiharu; Katori, Hidetoshi
• 署名单位: RIKEN; RIKEN; Japan Science & Technology Agency (JST); RIKEN; Tohoku University; Tohoku University; University of Tokyo
• 刊物名称: Nature
• ISSN/ISSBN: 0028-6976
• DOI: 10.1038/s41586-024-07296-1
• 发表日期: 2024-05-05
• 页码: 62-+
• 关键词: transition; thorium; energy; radii; state; decay

摘要

Thorium-229 (Th-229) possesses an optical nuclear transition between the ground state (Th-229g) and low-lying isomer (Th-229m). A nuclear clock based on this nuclear-transition frequency is expected to surpass existing atomic clocks owing to its insusceptibility to surrounding fields(1-5). In contrast to other charge states, triply charged Th-229 (Th-229(3+)) is the most suitable for highly accurate nuclear clocks because it has closed electronic transitions that enable laser cooling, laser-induced fluorescence detection and state preparation of ions(1,6-8). Although laser spectroscopic studies of Th-229(3+) in the nuclear ground state have been performed(8), properties of Th-229m(3+), including its nuclear decay lifetime that is essential to specify the intrinsic linewidth of the nuclear-clock transition, remain unknown. Here we report the trapping of Th-229m(3+) continuously supplied by a U-233 source and the determination of nuclear decay half-life of the isolated Th-229m(3+) to be 1,400(-300)(+600) s through nuclear-state-selective laser spectroscopy. Furthermore, by determining the hyperfine constants of Th-229m(3+), we reduced the uncertainty of the sensitivity of the Th-229 nuclear clock to variations in the fine-structure constant by a factor of four. These results offer key parameters for the Th-229(3+) nuclear clock and its applications in the search for new physics.