Absolute frequency measurement of the ¹S₀–³P₀ transition of ¹⁷¹Yb with a link to international atomic time

Abstract We report the absolute frequency measurement of the unperturbed optical clock transition 1S0–3P0 in 171Yb performed with an optical lattice frequency standard. Traceability to the International System of Units is provided by a link to International Atomic Time. The measurement result is 518 295 836 590 863.61(13) Hz with a relative standard uncertainty of , obtained operating our 171Yb optical frequency standard intermittently for 5 months. The 171Yb optical frequency standard contributes with a systematic uncertainty of .