Characterization of the ²²⁹Th nuclear clock transition in solid state hosts

The ^229mTh isomeric nuclear transition has the lowest known isomeric energy difference and is a prime candidate for a clock disciplined by an atomic nucleus. Atomic clocks based on electronic transitions have shown incredible stability as a timekeeping reference, and a clock based on a nuclear transition could be comparable. Furthermore, increasingly accurate measurements of the transition or comparisons with atomic transitions would explore new parameter spaces in looking for new physics, such as dark matter or temporal variations of fundamental constants.

After performing an absolute frequency measurement of the transition in a calcium fluoride crystal lattice using a vacuum ultraviolet frequency comb, we move on to characterizing the effects of the crystal on the clock transition. We will present the effects of temperature on the nuclear transition, and the frequency variation since first measurement.