Progress Towards a ²²⁹Th³⁺ Nuclear Clock

Atomic clocks are the most precise instruments in existence today, with current state of the art clocks achieving fractional accuracies at the level of 10^-18. Atomic clocks work by locking the frequency of a local oscillator (typically a laser) to an atomic transition. In general, the precision of an atomic clock is improved with higher frequency clock transitions and transitions which are less sensitive to external perturbations. To develop a next generation clock, it is natural then to seek a clock candidate which has a transition meeting both requirements. The ²²⁹Th³⁺ ion offers one such transition, having an anomalously low-energy (about 8 eV) nuclear isomer transition with wavelength of about 149 nm, just on the edge of what is experimentally achievable with VUV lasers. Furthermore, this clock transition is very narrow and is less sensitive to external perturbations due to the strong suppression of external field-shifts. Experimental progress towards the development of a next generation clock utilizing this ²²⁹Th³⁺ nuclear isomer transition will be presented.