Detection of the 5p – 4f orbital crossing and its optical clock transition in Pr⁹⁺

authored by

Hendrik Bekker, Anastasia Borschevsky, Zoltán Harman, Christoph H. Keitel, Thomas Pfeifer, Piet Oliver Schmidt, José R. Crespo López-Urrutia, Julian C. Berengut

Abstract

Recent theoretical works have proposed atomic clocks based on narrow optical transitions in highly charged ions. The most interesting candidates for searches of physics beyond the Standard Model are those which occur at rare orbital crossings where the shell structure of the periodic table is reordered. There are only three such crossings expected to be accessible in highly charged ions, and hitherto none have been observed as both experiment and theory have proven difficult. In this work we observe an orbital crossing in a system chosen to be tractable from both sides: Pr^{9 +}. We present electron beam ion trap measurements of its spectra, including the inter-configuration lines that reveal the sought-after crossing. With state-of-the-art calculations we show that the proposed nHz-wide clock line has a very high sensitivity to variation of the fine-structure constant, α, and violation of local Lorentz invariance; and has extremely low sensitivity to external perturbations.

Organisation(s)

Institute of Quantum Optics
QuantumFrontiers
CRC 1227 Designed Quantum States of Matter (DQ-mat)

External Organisation(s)

Max Planck Institute for Nuclear Physics
University of Groningen
National Metrology Institute of Germany (PTB)
University of New South Wales (UNSW)

Type

Article

Journal

Nature Communications

Volume

10

ISSN

2041-1723

Publication date

11.12.2019

Publication status

E-pub ahead of print

Peer reviewed

Yes

ASJC Scopus subject areas

Chemistry(all), Biochemistry, Genetics and Molecular Biology(all), Physics and Astronomy(all)

Electronic version(s)

https://doi.org/10.48550/arXiv.1910.09010 (Access: Open)
https://doi.org/10.1038/s41467-019-13406-9 (Access: Open)