Frequency ratio of the $^{229\mathrm{m}}$Th nuclear isomeric transition and the $^{87}$Sr atomic clock

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Main Authors: Zhang, Chuankun, Ooi, Tian, Higgins, Jacob S., Doyle, Jack F., von der Wense, Lars, Beeks, Kjeld, Leitner, Adrian, Kazakov, Georgy, Li, Peng, Thirolf, Peter G., Schumm, Thorsten, Ye, Jun
Format: Preprint
Published: 2024
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author Zhang, Chuankun
Ooi, Tian
Higgins, Jacob S.
Doyle, Jack F.
von der Wense, Lars
Beeks, Kjeld
Leitner, Adrian
Kazakov, Georgy
Li, Peng
Thirolf, Peter G.
Schumm, Thorsten
Ye, Jun
author_facet Zhang, Chuankun
Ooi, Tian
Higgins, Jacob S.
Doyle, Jack F.
von der Wense, Lars
Beeks, Kjeld
Leitner, Adrian
Kazakov, Georgy
Li, Peng
Thirolf, Peter G.
Schumm, Thorsten
Ye, Jun
contents 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 the first nuclear clock$^{3,4}$. However, quantum state-resolved spectroscopy of the $^{229m}$Th 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 $^{229}$Th nuclear clock transition in a solid-state CaF$_2$ host material and determine the absolute transition frequency. We stabilize the fundamental frequency comb to the JILA $^{87}$Sr clock$^2$ and coherently upconvert the fundamental to its 7th harmonic in the VUV range 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 $^{229}$Th nuclear clock transition and the $^{87}$Sr 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 clock and demonstrate the first comparison 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.
format Preprint
id arxiv_https___arxiv_org_abs_2406_18719
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Frequency ratio of the $^{229\mathrm{m}}$Th nuclear isomeric transition and the $^{87}$Sr atomic clock
Zhang, Chuankun
Ooi, Tian
Higgins, Jacob S.
Doyle, Jack F.
von der Wense, Lars
Beeks, Kjeld
Leitner, Adrian
Kazakov, Georgy
Li, Peng
Thirolf, Peter G.
Schumm, Thorsten
Ye, Jun
Atomic Physics
Nuclear Experiment
Optics
Quantum Physics
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 the first nuclear clock$^{3,4}$. However, quantum state-resolved spectroscopy of the $^{229m}$Th 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 $^{229}$Th nuclear clock transition in a solid-state CaF$_2$ host material and determine the absolute transition frequency. We stabilize the fundamental frequency comb to the JILA $^{87}$Sr clock$^2$ and coherently upconvert the fundamental to its 7th harmonic in the VUV range 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 $^{229}$Th nuclear clock transition and the $^{87}$Sr 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 clock and demonstrate the first comparison 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.
title Frequency ratio of the $^{229\mathrm{m}}$Th nuclear isomeric transition and the $^{87}$Sr atomic clock
topic Atomic Physics
Nuclear Experiment
Optics
Quantum Physics
url https://arxiv.org/abs/2406.18719