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Nuclear clock based on the Th v ion

V. V. Flambaum1,*, V. A. Dzuba1,†, and E. Peik2,‡

  • *Contact author: v.flambaum@unsw.edu.au
  • †Contact author: v.dzuba@unsw.edu.au
  • ‡Contact author: ekkehard.peik@ptb.de
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Phys. Rev. A 112, 023103 – Published 1 August, 2025

DOI: https://doi.org/10.1103/zcsk-3lw5

Abstract

We propose that a nuclear clock based on the Th v ion can surpass the accuracy of clocks built with other thorium ions. The Th4+ ion has a rigid closed-shell core with zero total electron angular momentum, suppressing frequency shifts from black-body radiation and stray external fields that act mainly on electrons. We calculate the energy shift of the nuclear clock transition frequency in Th229 due to the Coulomb field of atomic electrons and find a relative frequency difference of 2.8×10−7 between Th iv and Th v, 12 orders of magnitude larger than the projected 10−19 fractional uncertainty of a nuclear clock. We also perform calculations for Th v energy levels, ionization potential, static polarizability, quadratic Zeeman shift, and the black-body radiation shift of the nuclear line. Additionally, we determine the nuclear transition frequencies in two thorium ions and a neutral atom: νN=2,020,406.964(70)GHz in Th iii, νN=2,020,408.264(100)GHz in Th ii, and νN=2,020,408.364(100)GHz in Th i.

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Phys. Rev. A 112, 023103– Published 1 August, 2025
  • Received 5 March 2025
  • Accepted 1 July 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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