Hannover 2020 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 14: Poster Session - Atomic Physics II
A 14.15: Poster
Dienstag, 10. März 2020, 16:00–18:00, Empore Lichthof
Search for electronic bridge excitation of the nuclear clock isomer 229mTh — •David-Marcel Meier, Johannes Thielking, Gregor Zitzer, Maxim V. Okhapkin, and Ekkehard Peik — Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
The transition between the nuclear ground state and the low-energy isomer of 229Th has been proposed as a frequency reference for an optical clock of high accuracy, but its optical excitation is still pending.
We are investigating the excitation of the nucleus via electronic bridge/NEET processes, using two-photon laser excitation to access high-lying electronic levels in Th+ and in Th2+ [1]. About 100 excited electronic states of Th+ with energies ranging from 7.4 to 9.6 eV have been investigated for their fluorescence decay signals, without observing an indication of nuclear excitation. Experiments with selected levels of Th2+ have been performed using resolved hyperfine spectra [2] for a detection of the isomer. It is planned to revisit with improved statistics the narrower range of excitation energy 8.28(17) eV that has recently been obtained at LMU [3].
[1] D.-M. Meier et al., Phys. Rev. A 99, 052514 (2019).
[2] J. Thielking et al., Nature 556, 321-325 (2018).
[3] B. Seiferle et al., Nature 573, 243-246 (2019).