No abstract

Optical frequency measurements of the intercombination line (6s 2 ) 1 S0 −(6s6p) 3 P1 in the isotopes of ytterbium are carried out with the use of sub-Doppler fluorescence spectroscopy on an atomic beam. A dispersive signal is generated to which a master laser is locked, while frequency counting of an auxiliary beat signal is performed via a frequency comb referenced to a hydrogen maser. The relative separations between the lines are used to evaluate the 3 P1-level magnetic dipole and electric quadrupole constants for the fermionic isotopes. The center of gravity for the 3 P1 levels in 171 Yb and 173 Yb are also evaluated, where we find significant disagreement with previously reported values. These hyperfine constants provide a valuable litmus test for atomic many-body computations in ytterbium.