Absolute frequency measurements in Yb with 0 . 08 ppb uncertainty : Isotope shifts and hyperfine structure in the 399-nm 1 S 0 \ 1 P 1 line

We apply our recent technique of using a Rb-stabilized ring-cavity resonator to measure the absolute frequencies of various isotopic components in the 399-nm S0→ P1 line of Yb. For the transition in Yb, we obtain a value of 751 525 987.761 60 MHz, representing a relative uncertainty of 0.08 ppb. We also obtain the isotope shifts and hyperfine structure with 50 kHz precision, an order-of-magnitude improvement over our earlier measurements on this line. Our earlier work had helped in resolving some discrepancies among previous measurements, and the present work further confirms those results.