中国物理B ›› 2026, Vol. 35 ›› Issue (6): 64202-064202.doi: 10.1088/1674-1056/ae3e72

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Radiative decay of 229mTh in solid-state nuclear clocks

Zong-Heng Li(李宗珩) and Xu Wang(王旭)†   

  1. Graduate School, China Academy of Engineering Physics, Beijing 100193, China
  • 收稿日期:2025-10-27 修回日期:2026-01-07 接受日期:2026-01-28 发布日期:2026-06-15
  • 通讯作者: Yong Li E-mail:xwang@gscaep.ac.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12474484, U2330401, and 12088101).

Radiative decay of 229mTh in solid-state nuclear clocks

Zong-Heng Li(李宗珩) and Xu Wang(王旭)†   

  1. Graduate School, China Academy of Engineering Physics, Beijing 100193, China
  • Received:2025-10-27 Revised:2026-01-07 Accepted:2026-01-28 Published:2026-06-15
  • Contact: Yong Li E-mail:xwang@gscaep.ac.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12474484, U2330401, and 12088101).

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摘要： The $^{229}$Th isotope hosts an exceptionally low-energy nuclear transition in the vacuum ultraviolet range, making it a leading candidate for nuclear optical clocks. Recent laser excitation and fluorescence measurements in Th-doped crystals have demonstrated the feasibility of such clocks, yet the precise lifetime of the nuclear excited state remains uncertain. In this work, we build upon the well-established $n^3$ scaling of $M1$ nuclear decay rates, which describes how the radiative decay of a magnetic-dipole transition is modified by the refractive index $n$ of an isotropic and homogeneous medium. Our contribution unifies previously disparate experimental results on $^{229}$Th-doped crystals within a single theoretical framework and delineates the conditions under which the scaling remains valid. We further analyze the limitations of extracting vacuum lifetimes from existing solid-state measurements, highlighting the roles of non-radiative decay channels as well as surface and defect-induced effects, which can invalidate the simple $n^3$ rule under realistic experimental conditions. These insights open new possibilities for reducing interrogation times and improving the overall performance of nuclear clocks.

关键词: nuclear optical clock, thorium-229, quantum optics in dielectric

Abstract: The $^{229}$Th isotope hosts an exceptionally low-energy nuclear transition in the vacuum ultraviolet range, making it a leading candidate for nuclear optical clocks. Recent laser excitation and fluorescence measurements in Th-doped crystals have demonstrated the feasibility of such clocks, yet the precise lifetime of the nuclear excited state remains uncertain. In this work, we build upon the well-established $n^3$ scaling of $M1$ nuclear decay rates, which describes how the radiative decay of a magnetic-dipole transition is modified by the refractive index $n$ of an isotropic and homogeneous medium. Our contribution unifies previously disparate experimental results on $^{229}$Th-doped crystals within a single theoretical framework and delineates the conditions under which the scaling remains valid. We further analyze the limitations of extracting vacuum lifetimes from existing solid-state measurements, highlighting the roles of non-radiative decay channels as well as surface and defect-induced effects, which can invalidate the simple $n^3$ rule under realistic experimental conditions. These insights open new possibilities for reducing interrogation times and improving the overall performance of nuclear clocks.

Key words: nuclear optical clock, thorium-229, quantum optics in dielectric

中图分类号:  (Quantum optics)

  • 42.50.-p
76.80.+y (M?ssbauer effect; other γ-ray spectroscopy) 33.45.+x (M?ssbauer spectra)