EMMI Featured Talk: The Energy of the 229Th Nuclear Clock Transition

Incredibly precise nuclear clocks may soon outperform and replace the present atomic clocks that define the global time standard. The only known nuclear transition in the range of vacuum-ultraviolet (VUV) lasers occurs in 229Thorium and promises such a novel and unprecedently precise nuclear clock. The nuclear excited level is a metastable state and its most precise energy measurement has just recently provided the value 8.28 eV, allowing driving with VUV lasers. As a high-precision oscillator whose frequency is predominantly determined by the strong interaction, the 229Thorium transition also offers an increased precision for the determination of fundamental constant variations. The talk will follow the newest developments towards a nuclear clock from the experimental side and present new theoretical insights on the nuclear transition properties. In particular, the focus will lie on the very recent direct measurement of the nuclear transition energy via observation of the internal conversion decay channel [1]. [1] B. Seiferle et al., Nature 573, 243-246 (2019)