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Energy of the Th229 Nuclear Clock Isomer Determined by Absolute γ-ray Energy Difference

A. Yamaguchi, H. Muramatsu, T. Hayashi, N. Yuasa, K. Nakamura, M. Takimoto, H. Haba, K. Konashi, M. Watanabe, H. Kikunaga, K. Maehata, N. Y. Yamasaki, and K. Mitsuda
Phys. Rev. Lett. 123, 222501 – Published 26 November 2019

Abstract

The low-lying isomeric state of Th229 provides unique opportunities for high-resolution laser spectroscopy of the atomic nucleus. We determine the energy of this isomeric state by taking the absolute energy difference between the excitation energy required to populate the 29.2-keV state from the ground state and the energy emitted in its decay to the isomeric excited state. A transition-edge sensor microcalorimeter was used to measure the absolute energy of the 29.2-keV γ ray. Together with the cross-band transition energy (29.2keVground) and the branching ratio of the 29.2-keV state measured in a recent study, the isomer energy was determined to be 8.30±0.92eV. Our result is in agreement with the latest measurements based on different experimental techniques, which further confirms that the isomeric state of Th229 is in the laser-accessible vacuum ultraviolet range.

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  • Received 18 August 2019
  • Revised 12 October 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.222501

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Nuclear Physics

Authors & Affiliations

A. Yamaguchi1, H. Muramatsu2,*, T. Hayashi2, N. Yuasa3, K. Nakamura4, M. Takimoto5, H. Haba6, K. Konashi7, M. Watanabe7, H. Kikunaga8, K. Maehata3, N. Y. Yamasaki2, and K. Mitsuda2

  • 1Quantum Metrology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
  • 2Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-5210, Japan
  • 3Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan
  • 4Safety and Nuclear Security Administration Department, Japan Atomic Energy Agency, Chiyoda-ku, Tokyo 100-8577, Japan
  • 5Nuclear Fuel Cycle Engineering Laboratories, Japan Atomic Energy Agency, Naka-gun, Ibaraki 319-1194, Japan
  • 6Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0198, Japan
  • 7Institute for Materials Research, Tohoku University, Higashiibaraki-gun, Ibaraki 311-1313, Japan
  • 8Research Center for Electron Photon Science, Tohoku University, Sendai, Miyagi 982-0826, Japan

  • *Present address: National Aeronautics and Space Administration/Goddard Space Flight Center.

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Issue

Vol. 123, Iss. 22 — 29 November 2019

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