Bonn 2025 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 4: Precision Spectroscopy of Atoms and Ions II (joint session A/Q)
A 4.2: Vortrag
Montag, 10. März 2025, 17:30–17:45, HS PC
The Cryogenic Ion Trap Experiment for Laser Excitation of 229Th3+ at LMU — •Markus Wiesinger, Kevin Scharl, Georg Holthoff, Tamila Teschler, Mahmood I. Hussain, and Peter G. Thirolf — Ludwig-Maximilians-Universität München
The isomeric first excited state in 229Th with an excitation energy of only about 8.356 eV provides a unique opportunity for the development of an optical clock based on a nuclear transition – a nuclear clock. Attractive properties such as insensitivity to environmental conditions and long lifetime promise to enable new applications in fundamental physics, precision metrology, and geodesy.
At LMU work is ongoing towards the realization of a lifetime measurement of the isomeric state, and VUV spectroscopy of the nuclear transition in trapped 229Th3+ ions. To this end, a cryogenic ion trap has been set up and commissioned. As a prerequisite, nuclear state readout based on optical hyperfine spectroscopy of trapped Th3+ ions is currently being prepared.
In this talk we will focus on the experimental setup of the cryogenic ion trap: We will discuss our ion sources and ion loading procedures. We will show sympathetic laser cooling of 229Th3+ by Doppler-cooled 88Sr+ ions and the formation of mixed-species Coulomb crystals. The use of a radioactive 233U source will allow to conduct experiments not only with 229Th in the ground state, but also in the isomeric excited state (populated in 2% of the decays) – enabling a lifetime measurement without preceding laser excitation of the nuclear transition.
We acknowledge support by ERC (856415) and BaCaTec (7-2019-2).
Keywords: Thorium Nuclear Clock; Ion Traps; Sympathetic Cooling; Hyperfine Structure Spectroscopy