ISOTOPE SHIFTS AND HYPERFINE SPLITTINGS OF THE 398.8-NM YB I-LINE

We report the first observation to our knowledge of the 6s2 1S0-6s6p 1P1-degrees transition (398.8 nm) of Yb-168. The relative position of this spectral line was directly determined by using a laser sideband technique to simultaneously probe pairs of lines. The hyperfine structure of Yb-171 and the isotope shifts of Yb-170, Yb-171, and Yb-174 were determined to an accuracy of better than 6 MHz and found to differ by as much as 23 MHz from previous results. By using photon-burst spectroscopy to carry out these measurements we obtained subnatural linewidths and fully resolved the Yb-170 and Yb-171 lines, which otherwise overlap in fluorescence.