Michael Bartokos

Editor’s summary Abstract Supplementary Materials References and Notes Information & Authors Metrics & Citations Check Access References Figures Tables Media Share Editor’s summary Atomic clocks are the world’s most precise timekeepers, but nuclear clocks, which depend on transitions between nuclear energy levels, might prove even more useful. Scientists have long focused on a particular nucleus, that of thorium-229, because its transitions are compatible with laser frequencies.

Abstract Nuclear laser spectroscopy at the 10−12 precision level (Nature 633.8028 (2024): 63–70) determined the fractional change in the nuclear quadrupole moment of 229Th upon excitation, ΔQ0/Q0 = 1.791(2)%. Such high-accuracy nuclear parameters enable stringent tests and refinement of 229Th nuclear models.

Abstract The radioisotope thorium-229 (229Th) is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by vacuum ultraviolet (VUV) lasers and 229Th has been proposed as a reference transition for ultra-precise nuclear clocks. To assess the feasibility and performance of the nuclear clock concept, time-controlled excitation and depopulation of the 229Th isomer are imperative.