Absolute frequency measurement of the 1 S 0 – 3 P 0 transition of 171 Yb with a link to international atomic time

We report the absolute frequency measurement of the unperturbed optical clock transition 1 S 0 – 3 P 0 in 171 Yb 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 171 Yb optical frequency standard intermittently for 5 months. The 171 Yb optical frequency standard contributes with a systematic uncertainty of .