Precise measurements of UV atomic lines: Hyperfine structure and isotope shifts in the 398.8 nm line of Yb

We demonstrate a technique for frequency measurements of UV transitions with sub-MHz precision. The frequency is measured using a ring-cavity resonator whose length is calibrated against a reference laser locked to the D 2 line of 87 Rb. We have used this to measure the 398.8 nm 1 S 0 ↔ 1 P 1 line of atomic Yb. We report isotope shifts of all the seven stable isotopes, including the rarest isotope 168 Yb. We have been able to resolve the overlapping 173 Yb ( F = 3/2) and 172 Yb transitions for the first time. We also obtain high-precision measurements of the excited-state hyperfine structure in the odd isotopes, 171 Yb and 173 Yb. The measurements resolve several discrepancies among earlier measurements.