近日，德国布伦瑞克联邦物理技术研究所（PTB）Peik, E.团队报道了钍-229核的连续波激光吸收光谱。相关论文于2026年9月16日发表在《自然》杂志上。

钍-229（Th-229）中的低能核跃迁已在掺钍晶体中通过激光激发，为通向高度稳定且坚固的固态光学核钟开辟了道路。所需的148纳米波长激光辐射迄今一直使用脉冲激光系统产生，而其中只有一小部分入射光子与窄核跃迁共振。

研究组表明，可以用连续波（CW）、窄带宽、固态激光源在亚纳瓦功率下激发原子核，并且可以以吸收而非荧光方式检测核共振信号。这从检测过程中消除了缓慢的核荧光衰变，从而允许以快速信号采集进行时钟运行。研究组表征了氟化钙（CaF₂）晶体中两种不同的钍中心，并测量了它们之间的同质异能位移。其中一个中心显示出非常小的静态电场晶体场梯度 <0.1 V Å^-2，而先前观察到的梯度在100 V Å^-2范围内。这表明该中心中围绕钍核的离子具有高度对称性，有望产生几乎不依赖于晶格间距的核共振线。

附：英文原文

Title: Continuous-wave laser absorption spectroscopy of the thorium-229 nucleus

Author: Morawetz, I., Riebner, T., De Col, L. Toscani, Schneider, F., Sempelmann, N., Schaden, F., Bartokos, M., Kazakov, G. A., Lahs, S., Beeks, K., Gerstenecker, B., Grneis, A., Pimon, M., Schumm, T., Lal, V., Zitzer, G., Petrov, V., Tiedau, J., Okhapkin, M. V., Peik, E.

Issue&Volume: 2026-09-16

Abstract: The low-energy nuclear transition in thorium-229 (Th-229) has been excited in thorium-doped crystals with laser light1,2,3, opening the path towards a highly stable and robust solid-state optical nuclear clock4. The required laser radiation at 148-nm wavelength has so far been produced using pulsed laser systems, in which only a small fraction of the incident photons has been resonant with the narrow nuclear transition. Here we show that the nucleus can be excited with a continuous-wave (CW), narrow-bandwidth, solid-state laser source5 at sub-nanowatt power and that the nuclear resonance signal can be detected in absorption rather than fluorescence. This eliminates the slow nuclear fluorescence decay from the detection process, allowing for clock operation with fast signal acquisition. We characterize two different thorium centres in a calcium fluoride (CaF2) crystal and measure the isomeric shift between them. One of the centres shows a very small static electric crystal field gradient <0.1V2 compared with gradients in the range of 100V2 observed previously3,6. This indicates a centre with high symmetry of the ions surrounding the thorium nucleus, promising nuclear resonance lines that are nearly independent of the lattice spacing.

DOI: 10.1038/s41586-026-11011-7

Source: https://www.nature.com/articles/s41586-026-11011-7