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

We report the absolute frequency measurement of the unperturbed optical clock transition S-1(0)-P-3(0) in Yb-171 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 Yb-171 optical frequency standard intermittently for 5 months. The Yb-171 optical frequency standard contributes with a systematic uncertainty of 2.8 x 10(-17).