Knowledge Bank

High resolution excitation spectra of the $A1\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2-X2\Sigma +$ and $A2\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2-X2\Sigma +$ transitions of YbF have been obtained and the spectra of several isotopomers have been analysed. Among the results to be discussed will be the (1) A doubling in the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2$ states and its correlation with the $B2\Sigma +$ state, (2) the spin rotation splitting in the $X2\Sigma +$ state and the anomalous splitting in the v = 1 level, (3) the perturbation in the v = 1 level of $A1\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2$ and the analysis of the perturbing state. The experimental results will be discussed in terms of predictions of ligand field theory calculations.