Optical Zeeman Spectroscopy of Ytterbium Monofluoride, YbF

The Zeeman-induced shifts and splittings of low-<i>J</i> lines in the <sup>O</sup>P<sub>12</sub> branch of the (0,0) band of the A<sup>2</sup>Π<sub>1/2</sub>−X<sup>2</sup>Σ<sup>+</sup> electronic transition of a cold molecular beam sample of ytterbium monofluoride, YbF, have been recorded. The Zeeman spectra for the <sup>171</sup>YbF, <sup>172</sup>YbF, and <sup>174</sup>YbF isotopologues have been analyzed using a standard effective Hamiltonian approach. The magnetic <i>g</i>-factors determined for the A<sup>2</sup>Π<sub>1/2</sub>(<i>v</i> = 0) state are rationalized using the predicted and observed electronic state distribution. The observed Zeeman tuning of the levels in the A<sup>2</sup>Π<sub>1/2</sub>(<i>v</i> = 0) state is unexpectedly large; this is caused by mixing with the B<sup>2</sup>Σ<sup>+</sup> state.