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Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock
Nature ( IF 50.5 ) Pub Date : 2024-09-04 , DOI: 10.1038/s41586-024-07839-6
Chuankun Zhang 1, 2, 3 , Tian Ooi 1, 2, 3 , Jacob S Higgins 1, 2, 3 , Jack F Doyle 1, 2, 3 , Lars von der Wense 1, 2, 3, 4 , Kjeld Beeks 5, 6 , Adrian Leitner 5 , Georgy A Kazakov 5 , Peng Li 7 , Peter G Thirolf 8 , Thorsten Schumm 5 , Jun Ye 1, 2, 3
Affiliation  

Optical atomic clocks1,2 use electronic energy levels to precisely keep track of time. A clock based on nuclear energy levels promises a next-generation platform for precision metrology and fundamental physics studies. Thorium-229 nuclei exhibit a uniquely low-energy nuclear transition within reach of state-of-the-art vacuum ultraviolet (VUV) laser light sources and have, therefore, been proposed for construction of a nuclear clock3,4. However, quantum-state-resolved spectroscopy of the 229mTh isomer to determine the underlying nuclear structure and establish a direct frequency connection with existing atomic clocks has yet to be performed. Here, we use a VUV frequency comb to directly excite the narrow 229Th nuclear clock transition in a solid-state CaF2 host material and determine the absolute transition frequency. We stabilize the fundamental frequency comb to the JILA 87Sr clock2 and coherently upconvert the fundamental to its seventh harmonic in the VUV range by using a femtosecond enhancement cavity. This VUV comb establishes a frequency link between nuclear and electronic energy levels and allows us to directly measure the frequency ratio of the 229Th nuclear clock transition and the 87Sr atomic clock. We also precisely measure the nuclear quadrupole splittings and extract intrinsic properties of the isomer. These results mark the start of nuclear-based solid-state optical clocks and demonstrate the first comparison, to our knowledge, of nuclear and atomic clocks for fundamental physics studies. This work represents a confluence of precision metrology, ultrafast strong-field physics, nuclear physics and fundamental physics.



中文翻译:


229mTh核异构跃迁与87Sr原子钟的频率比



光学原子钟1,2使用电子能级来精确记录时间。基于核能水平的时钟有望为精密计量和基础物理研究提供下一代平台。钍 229 原子核在最先进的真空紫外 (VUV) 激光光源的照射范围内表现出独特的低能核跃迁,因此被提议用于构建核钟3,4 。然而,尚未对229m Th 异构体进行量子态分辨光谱以确定潜在的核结构并与现有原子钟建立直接频率连接。在这里,我们使用VUV频率梳直接激发固态CaF 2主体材料中的窄229 Th核时钟跃迁并确定绝对跃迁频率。我们将基波频率梳稳定到 JILA 87 Sr 时钟2 ,并通过使用飞秒增强腔将基波相干上变频到 VUV 范围内的第七谐波。这种VUV梳在核能级和电子能级之间建立了频率联系,使我们能够直接测量229 Th核钟跃迁和87 Sr原子钟的频率比。我们还精确测量核四极分裂并提取异构体的内在特性。这些结果标志着基于核的固态光学钟的开始,并展示了据我们所知,用于基础物理研究的核钟和原子钟的首次比较。 这项工作代表了精密计量学、超快强场物理、核物理和基础物理的融合。

更新日期:2024-09-04
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