Mainz 2026 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 13: Nuclear Clocks
Q 13.3: Vortrag
Montag, 2. März 2026, 17:30–17:45, P 11
Towards lifetime measurement of the nuclear clock isomer 229mTh3+ via hyperfine laser spectroscopy in a cryogenic Paul trap — •Georg Holthoff, Kevin Scharl, Tamila Teschler, Daniel Moritz, Markus Wiesinger, and Peter G. Thirolf — Ludwig-Maximilians-Universität München
The Thorium-229 isomer with its uniquely low lying 8.4 eV nuclear excited state is the so far most promising candidate for a nuclear frequency standard (’nuclear clock’). Due to the long lifetime of the excited state (ca. 2000 s in vacuum, expected to be measured precisely in our experiment), thus low emission rate, and ca. 148.4 nm VUV wavelength of the emitted photon, direct fluorescence detection is extremely difficult in the trapped ion approach. At LMU Munich, determining if nuclear excitation of 229mTh3+ in our cryogenic Paul trap has occurred will therefore be performed via a double-resonance method as proposed in 2003 by Peik et al. For this we discuss predictions of the hyperfine structure of the ground and isomeric state as well as the isomer shift. Ongoing experimental work on hyperfine spectroscopy of sympathetically laser-cooled 229mTh3+ will also be presented. The choice of hyperfine transitions to differentiate the two states and the influence of their addressing scheme is discussed for both 690 nm and 984 nm lasers. Furthermore, experimental results for different hyperfine addressing schemes using EOMs driven by voltage controlled oscillators (VCOs) are discussed. Supported by the European Research Council (ERC): Grant 856415.
Keywords: Nuclear Clock; Hyperfine Spectroscopy; Thorium 229 Isomer; Trapped Ions