Search Efforts for the ²²⁹Th Low-Lying Nuclear Transition*

In the ²²⁹Th nucleus, there exists a relatively low-energy isomeric state that is 8.338(24) eV above the nuclear ground state [1]. It has been noted that the characteristics of this transition make it a promising platform for an ultra-high precision nuclear clock [2]. Due to its low energy, this state can be directly excited with a laser that is tuned into the vacuum-ultraviolet (VUV) spectrum. Our work has centered around exciting this transition using a tunable dye laser system in order to more accurately resolve the uncertainty in the transition energy to several GHz. We will report on our recent progress towards addressing the ²²⁹Th nucleus and our current excitation wavelength scan inside the 90% confidence interval of the isomeric energy [3].

[1] Kraemer, S. et al. Observation of the Radiative Decay of the ²²⁹Th Nuclear Clock Isomer. ArXiv (2022)

[2] Campbell, C. et al. Phys. Rev. Lett. 108, 120802 (2012)

[3] Jeet, J. et al. Phys. Rev. Lett. 114, 253001 (2015)