The helion charge radius from laser spectroscopy of muonic helium-3 ions

• DOI: 10.1126/science.adj2610
• Publication Date: 2025-05-23T12:52:21Z
• Authors: Karsten Schuhmann; Luis M. P. Fernandes; François Nez; Marwan Abdou Ahmed; Fernando D. Amaro; Pedro Amaro; François Biraben; Tzu-Ling Chen; Daniel S. Covita; Andreas J. Dax; Marc Diepold; Beatrice Franke; Sandrine Galtier; Andrea L. Gouvea; Johannes Götzfried; Thomas Graf; Theodor W. Hänsch; Malte Hildebrandt; Paul Indelicato; Lucile Julien; Klaus Kirch; Andreas Knecht; Franz Kottmann; Julian J. Krauth; Yi-Wei Liu; Jorge Machado; Cristina M. B. Mo...; Françoise Mulhauser; Boris Naar; Tobias Nebel; Joaquim M. F. dos...; José Paulo Santos; Csilla I. Szabo; David Taqqu; João F. C. A. Veloso; Andreas Voss; Birgit Weichelt; Aldo Antognini; Randolf Pohl
• Keywords: Charge radius; Lamb shift; Exotic atom; Effective nuclear charge

Hydrogen-like light muonic ions, in which one negative muon replaces all of the electrons, are extremely sensitive probes nuclear structure. Using pulsed laser spectroscopy, we have measured three 2 S -2 P transitions helium-3 (μ 3 He + ) ion, an ion formed by a and bare nucleus. This allowed us to extract Lamb shift, fine structure splitting, -hyperfine splitting μ . Comparing these measurements with theory, determined root-mean-square charge radius helion ( nucleus) be r h = 1.97007(94) fm, good agreement value from elastic electron scattering but factor 15 more accurate. Our results represent benchmarks for few-nucleon theories open way precision quantum electrodynamics tests atoms ions.