LASER SPECTROSCOPY OF THE LANTHANIDE MONOFLUORIDES - THE GROUND-STATE CONFIGURATION OF HOLMIUM FLUORIDE

Observations of first lines in the branches of fluorescence excitation spectra of the A-X system of HoF and resolved fluorescence spectra of the B-X system have established that Ω(A) = 9, Ω(B) = 8, and Ω(X) = 8. Ligand field calculations predict three low-lying Ln+ configurations, 4fN-16s2, 4fN6s, and 4fN-15d6s, for the low-lying states of the lanthanide monofluorides (LnF). The Ω = 8 assignment for the X state establishes that the ground state configuration of HoF is 4f106s2. Vibrational frequencies of ωe ∼ 600, 550, 500 cm-1, respectively, are suggested as diagnostics of the fN-1s2, fN-1sd, and fNs superconfigurational character for all low-lying states of all LnF molecules. A rotational analysis of the A-X system has been performed and the molecular parameters are presented. Hyperfine structure is not resolved but the hyperfine widths of the broadened lines (P > Q > R) indicates that the hyperfine splitting is larger in the A than in the X state. © 1992.