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Q: Fachverband Quantenoptik und Photonik
Q 27: Poster – Precision Spectroscopy of Atoms and Ions (joint session A/Q)
Q 27.29: Poster
Tuesday, March 3, 2026, 17:00–19:00, Philo 1. OG
Internal conversion of Thorium-229 upon laser photo-excitation — •Marc Seitz1, Daniel Moritz2, Shengfeng Zeng3, Francesca Calegari1, Hannes Hübener4, Umberto de Giovannini4, Peter G. Thirolf2, and Andrea Trabattoni1 — 1Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany — 2LMU München, Fakultät für Physik, 85748 Garching bei München, Germany — 3Shenzhen Geim Graphene Center, Institue of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China — 4Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
The low-energy isomeric transition of Thorium-229 and its dominant internal-conversion (IC) decay channel provide a unique platform for studying electron-nucleus interactions. Prior work indicates that the IC decay can be strongly influenced by the electronic environment. Here, we investigate the IC decay of Th-229 in the presence of an ultraviolet (UV) laser field. Thorium atoms are deposited on a high-bandgap surface to minimize hybridization with surface states. A UV laser resonantly promotes an electron to the lowest excited atomic state prior to nuclear decay. The resulting IC electrons are detected via time-of-flight spectroscopy. By comparing laser-on and laser-off measurements, we identify changes in the IC decay dynamics induced by photo-excitation. This constitutes, to our knowledge, the first experimental study of laser-perturbed Th-229m IC nuclear decay.
Keywords: Thorium-229; Internal Conversion; Nuclear decay; Photo-perturbation; Time-of-flight spectroscopy