Quantum Electrodynamics in Strong Electromagnetic Fields: Substate Resolved Kα Transition Energies in Heliumlike Uranium

• Published in: Physical review letters Vol. 134; no. 15; p. 153001
• Main Authors: Pfäfflein, Ph, Weber, G, Allgeier, S, Andelkovic, Z, Bernitt, S, Bondarev, A I, Borovik, A, Duval, L, Fleischmann, A, Forstner, O, Friedrich, M, Glorius, J, Gumberidze, A, Hahn, Ch, Herfurth, F, Hengstler, D, Herdrich, M O, Hillenbrand, P-M, Kalinin, A, Kiffer, M, Kröger, F M, Kubullek, M, Kuntz, P, Lestinsky, M, Litvinov, Yu A, Löher, B, Menz, E B, Over, T, Petridis, N, Ringleb, S, Sidhu, R S, Spillmann, U, Trotsenko, S, Warczak, A, Zhu, B, Enss, Ch, Stöhlker, Th
• Format: Journal Article
• Language: English
• Published: United States 18.04.2025
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.134.153001

Using novel metallic magnetic calorimeter detectors at the CRYRING@ESR, we recorded x-ray spectra of stored and electron cooled heliumlike uranium (U^{90+}) with an unmatched spectral resolution of close to 90 eV. This allowed for an accurate determination of the energies of all four components of the Kα transitions in U^{90+}. We find good agreement with state-of-the-art bound-state QED calculations for the strong-field regime. Our results do not support any systematic deviation between experiment and theory in heliumlike systems, the presence of which was subject of intense debates in recent years.