Knowledge Bank

The use of vibration frequencies, $\Omega$ assignments and energy linkages as diagnostics of the superconfigurational parentage of low lying electronic states of lanthanide oxides is well established. The same techniques have now been extended to the lanthanide monofluorides, for which three low lying superconfigurations, $4fN-16s2$, $4fN6s$ and $4fN-15d6s$, all centered on the metal ion ($M+$), have bean predicted. Results of early experiments, using various laser spectroscopic techniques, will be surveyed. Among the experiments to be discussed will be (a) laser excitation and resolved fluorescence spectroscopy of HoF and (b) sub-Doppler excitation spectroscopy and resolved fluorescence of DyF.These experiments have established the ground state superconfigurations for both molecules and provided linkages, both between and within superconfigurations, for DyF. Results for these and other molecules will be discussed in relation to predictions of ligand field theory.