Absolute frequency measurements in Yb with $0.08\phantom\rule0.3em0ex\mathrmppb$ uncertainty: Isotope shifts and hyperfine structure in the $399\text-\mathrmnm$ $^1S_0$\rightarrow$^1P_1$ 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 1S0â1P1 line of Yb. For the transition in 174Yb, 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.