We propose optical precision spectroscopy of ultra-cold atomic hydrogen referenced to an optical atomic clock. H atoms will be trapped and cooled in the magnetic trap recently built at UTU. Evaporative cooling will be used to produce H gas with velocities of <50 cm/s. At these conditions, two-photon 1S-2S spectroscopy of the atoms will provide an unprecedented level of precision. The UV laser system for these experiments will be constructed at UTU and characterized by VTT. The laser will be stabilized to an ultra-stable Fabry-Perot resonator and referenced to the optical clock at VTT utilizing a coherent 160-km fiber link between UTU (Turku) and VTT (Espoo). The efforts on improvement of H spectroscopy together with the traceability to the best optical clocks will contribute to research in physics beyond the standard model, search for dark matter, and verification of the stability of fundamental constants.

2026

2030