Absolute frequencies of cooling and pumping transitions for Thulium optical lattice clock and cold gas studies

Abstract

Optical atomic clock based on 1.14 µm transition in neutral thulium is considered as one of the promising candidates for compact and robust transportable system owing to its very low sensitivity to external electric and magnetic fields. Besides optical clocks, cold Tm atoms are used in Bose-Einstein condensation studies, cold collision physics and quantum simulators. In this work, we report measurements of the absolute frequencies of the two cooling transitions at 410.6 nm and 530.7 nm, and the optical pumping transition at 418.8 nm. Using accurate laser spectroscopy of these transitions in an ensemble of cold thulium atoms, we measured corresponding frequencies using a hydrogen maser-referenced optical frequency comb. Transition frequencies were determined with an uncertainty of about one tenth of the corresponding natural linewidth which is good enough for straightforward cooling and pumping of atoms. Our results are useful for existing experiments with cold thulium atoms and even more demanded for new projects.