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Q: Fachverband Quantenoptik und Photonik

Q 25: Precision Spectroscopy of Atoms and Ions II (joint session A/Q)

Q 25.3: Talk

Tuesday, March 3, 2026, 11:45–12:00, N 3

Precision X-Ray Spectroscopy of Kα transitions in He-like Uranium using Metallic Magnetic Calorimeter Detectors — •Daniel A. Schnauß-Müller^{1, 2, 3}, Johanna H. Walch^{1, 2, 3}, Philip Pfäfflein^{1, 2, 3}, Marc O. Herdrich^{1, 2}, Michael Lestinsky², Daniel Hengstler⁴, Andreas Fleischmann⁴, Christian Enss⁴, Günter Weber^{1, 2}, and Thomas Stöhlker^{1, 2} — ¹Helmholtz Institut, Jena — ²GSI, Darmstadt — ³Friedrich-Schiller-Universität, Jena — ⁴Kirchhoff Institut, Heidelberg

He-like ions, as the simplest atomic multibody system, provide a unique testing ground for the interplay of the effects of electron-electron correlations and quantum electrodynamics (QED). Of particular interest are heavy highly charged systems, where inner shell electrons are exposed to extremely high field strengths. For L to K-transitions, experiments with ions at nuclear charge states Z > 54 where not available until now. Two X-ray spectroscopy studies of He-like uranium ions have been performed at the electron cooler of the storage ring CRYRING@ESR at GSI Darmstadt, using novel detectors of the maXs series, developed within the SPARC collaboration. Those detectors are able to measure photons from a few keV up to over 100 keV allowing the simultaneous investigation of Balmer-like and Kα transitions. The achieved spectral resolution of better than 90 eV at X-ray energies close to 100 keV reveals the substructure of the Kα1 and Kα2 lines for the first time. The result of this experiment and the first insights of a rerun this year are presented in the talk.

Keywords: Metallic Magnetic Calorimeter; precision X-ray spectroscopy; bound-state QED; storage ring