Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock
成果类型：
Article
署名作者：
Zhang, Chuankun; Ooi, Tian; Higgins, Jacob S.; Doyle, Jack F.; von der Wense, Lars; Beeks, Kjeld; Leitner, Adrian; Kazakov, Georgy A.; Li, Peng; Thirol, Peter G.; Schumm, Thorsten; Ye, Jun
署名单位：
University of Colorado System; University of Colorado Boulder; National Institute of Standards & Technology (NIST) - USA; University of Colorado System; University of Colorado Boulder; Technische Universitat Wien; University of Munich; Johannes Gutenberg University of Mainz; Swiss Federal Institutes of Technology Domain; Ecole Polytechnique Federale de Lausanne
刊物名称：
Nature
ISSN/ISSBN：
0028-5023
DOI：
10.1038/s41586-024-07839-6
发表日期：
2024-09-05
页码：
63-70
关键词：
摘要：
Optical atomic clocks(1,2) 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 clock(3,4). However, quantum-state-resolved spectroscopy of the Th-229m 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 Th-229 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 Sr-87 clock(2) 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 Th-229 nuclear clock transition and the Sr-87 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 frst comparison, to our knowledge, of nuclear and atomic clocks for fundamental physics studies. This work represents a confuence of precision metrology, ultrafast strong-feld physics, nuclear physics and fundamental physics.