100 Years of Nuclear Isomers

The exceptionally low energy of the isomeric first excited nuclear state of ${}^{229}$Th, which has recently been constrained to 8.28$\pm$0.17 eV (i.e. $\lambda$=149.7$\pm$3.1 nm) [1], allows for direct laser excitation with current technology. This offers the unique opportunity to develop a nuclear clock capable of competing or even outperforming existing atomic clocks. One of the next steps towards the realization of such a clock is the determination of the ${}^{229}$Th isomer's ionic lifetime (theoretically expected to range between ${10}^3-{10}^4$ seconds) via hyperfine spectroscopy. In order to achieve the required long ion storage time, a cryogenic Paul-trap with a corresponding mass-selective ion guide system has been set up at LMU Munich. The talk will present this new experimental platform.

This work was supported by DFG (Th956/3-2) as well as by the European Union’s Horizon 2020 research and innovation program under grant agreement 6674732 "nuClock" and the ERC Synergy Grant "ThoriumNuclearClock".

[1] B. Seiferle et al., Nature 573, 243 (2019).