Absolute frequencymeasurement of the S-2(1/2) - F-2(7/2) optical clock transition in Yb-171(+) with an uncertainty of 4 x 10(-16) using a frequency link to international atomic time

摘要

The highly forbidden S-2(1/2) - F-2(7/2) electric octupole transition in Yb-171(+) is a potential candidate for a redefinition of the SI second. Wepresent a measurement of the absolute frequency of this optical transition, performed using a frequency link to International Atomic Time to provide traceability to the SI second. The Yb-171(+) optical frequency standard was operated for 76% of a 25-day period, with the absolute frequency measured to be 642 121 496 772 645.14(26) Hz. The fractional uncertainty of 4.0 x 10(-16) is comparable to that of the best previously reported measurement, which was made by a direct comparison to local caesium primary frequency standards.