M. Bartokos

Abstract The laser-accessible nuclear transition in the thorium-229 isotope has been identified as a candidate for realizing an optical nuclear clock1 that might outperform current optical clocks based on electron-shell transitions in atoms or ions2. It is expected to be more robust against external perturbations3,4 and to provide enhanced sensitivity in clock-based tests of the fundamental principles of physics5,6.

Abstract The low-energy nuclear transition in thorium-229 (Th-229) has been excited in thorium-doped crystals with laser light1,2,3, opening the path towards a highly stable and robust solid-state optical nuclear clock4. The required laser radiation at 148-nm wavelength has so far been produced using pulsed laser systems, in which only a small fraction of the incident photons has been resonant with the narrow nuclear transition.