Speaker
Description
Since at least the first laser excitations of the $^{229}$Th nucleus in 2024, $^{229}$Th nuclear clocks is the talk of the town [1-3]. In the HiThor project an alternative scenario for $^{229}$Th studies is pursued that is based on $^{229}$Th$^{q+}$ ions in their highest charge states (q»1). Key to the HiThor programm is H-like $^{229}$Th$^{89+}$ that exhibits an effect termed nuclear hyperfine mixing (NHM). In $^{229}$Th$^{89+}$ and other highly charged $^{229}$Th-ions with unpaired valence electrons strong magentic fields due to the electrons at the site of the nucleus lead to hyperfine interaction (HFI). In addition to the common hyperfine splitting (HFS), in $^{229}$Th$^{89+}$ the HFI mixes the $F=2$ states of ground and nuclear metastable state, introduces a further small energy shift but most noteworthy broadens the nuclear decay width by more than five orders of magnitude, from about 45 mins down to a few ten milliseconds. Due this broader width the probaility for laser excitation is accordingly enhenced and enables VUV-laser spectrosocpy also with small samples or even single ions using present VUV-laser technology. NHM can thus be seen as a key technology to develop nuclear clocks with very „simple“ electronic configurations and, ultimately, to pave the road towards a no-electron nuclear clock consiting solely of the nucleus itself, $^{229}$Th$^{90+}$.
In the presentation, the status of the project and the roadmap towards the realization of HiThor at the ESR / HITRAP complex at the GSI-Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany is discussed.
Acknowledgement: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 101142155).
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