Toward XUV frequency comb spectroscopy of the 1 S–2 S transition in

Jorge Moreno; Fabian Schmid; Johannes Weitenberg; Savely G. Karshenboim; Theodor W. Hänsch; Thomas Udem; Akira Ozawa

doi:10.1140/epjd/s10053-023-00645-1

2024 Impact factor 1.5

Atomic, Molecular, Optical and Plasma Physics

Precision Physics of Simple Atomic Systems

Open Access

Eur. Phys. J. D (2023) 77: 67
https://doi.org/10.1140/epjd/s10053-023-00645-1

Regular Article - Atomic Physics

Toward XUV frequency comb spectroscopy of the 1 S–2 S transition in ${He}^{+}$ $\hbox {He}^+$

Jorge Moreno¹, Fabian Schmid¹, Johannes Weitenberg¹^,2, Savely G. Karshenboim¹^,3, Theodor W. Hänsch¹^,3, Thomas Udem¹^,3 and Akira Ozawa¹^g

¹ Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748, Garching, Germany
² Fraunhofer-Institut für Lasertechnik ILT, Steinbachstraße 15, 52074, Aachen, Germany
³ Fakultät für Physik, Ludwig-Maximilians-Universität München, Schellingstraße 4, 80799, Munich, Germany

^g akira.ozawa@mpq.mpg.de

Received: 5 February 2023
Accepted: 31 March 2023
Published online: 24 April 2023

Abstract

The energy levels of hydrogen-like atoms and ions are accurately described by bound-state quantum electrodynamics (QED). ${He}^{+}$ $\hbox {He}^{+}$ ions have a doubly charged nucleus, which enhances the higher-order QED contributions and makes them interesting for precise tests of QED. Systematic effects that currently dominate the uncertainty in hydrogen spectroscopy, such as the second-order Doppler shift and time-of-flight broadening, are largely suppressed by performing spectroscopy on trapped and cooled ${He}^{+}$ $\hbox {He}^{+}$ ions. Measuring a transition in ${He}^{+}$ $\hbox {He}^{+}$ will extend the test of QED beyond the long-studied hydrogen. In this article, we describe our progress toward precision spectroscopy of the 1 S–2 S two-photon transition in ${He}^{+}$ $\hbox {He}^{+}$ . The transition can be excited by radiation at a wavelength of 60.8 nm generated by a high-power infrared frequency comb using high-order harmonic generation (HHG). The ${He}^{+}$ $\hbox {He}^{+}$ ions are trapped in a Paul trap and sympathetically cooled with laser-cooled ${Be}^{+}$ $\hbox {Be}^{+}$ ions. Our recently developed signal detection scheme based on secular-scan spectrometry is capable of detecting ${He}^{+}$ $\hbox {He}^{+}$ excitation with single-event sensitivity.

Precision Physics of Simple Atomic Systems

Guest editors: Paolo Crivelli, Krzysztof Pachucki, Wim Ubachs, Thomas Udem, and Stefan Ulmer.

© The Author(s) 2023

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