Speaker
Description
Thorium-229 possesses an exceptionally low-energy isomeric state (~8.356 eV, $^{229m}$Th), which can be excited using the state-of-the-art tabletop lasers operating in the vacuum ultraviolet (VUV) region [1–3]. The transition from the ground state to $^{229m}$Th is considered a clock transition, offering the potential for a nuclear clock that could surpass current optical atomic clocks in robustness and performance. Such a nuclear clock could be the next-generation platform for probing new physics beyond the Standard Model. To study this charming transition, we utilized the high-brilliance synchrotron radiation at SPring-8 (Hyogo, Japan) and developed an experimental setup capable of manipulating the three lowest nuclear states of thorium-229 when they are doped into a CaF$_2$ crystalline lattice [4]. Our experiment reveals that the lifetime of $^{229m}$Th in the CaF$_2$ crystal could be shortened by X-ray irradiation, and we called this phenomenon the ``isomer quenching'' [5]. In this presentation, we will introduce our new findings, demonstrating that crystal temperature significantly affects the efficiency of isomer quenching. Additionally, observations of the isomer yield and crystal luminescence suggest a possible interaction process between the thorium nucleus and the crystal environment.
