Laser spectroscopy of the B[21.68]8-X8, B′[21.65]8-X8 and C[22.3]7-X27 transitions of holmium monofluoride

The spectrum of holmium monofluoride (HoF) in the blue (420-480 nm) region has been studied using laser-induced fluorescence. Previous work [J. Phys. B 7 (1974) L234] had assigned several bands in this region to the B8-X8 transition. By obtaining wavelength selected laser excitation spectra at high resolution and rotationally analyzing seven bands in this region, we have shown that not all the bands previously assigned to the B8-X8 system belong to the same electronic transition and have identified three separate transitions which we have labelled B8-X8, B′8-X8, and C7-X27. Preliminary low resolution dispersed fluorescence spectra have shown several excited states at energies greater than 4000 cm−1 above the ground state and, though not all could be assigned, ligand field theory calculations are consistent with assigning them to the first excited spin-orbit component of the Ho+(4f106s2)F− ground state configuration or to the first excited configuration, Ho+(4f116s)F−. The results of the dispersed fluorescence experiments also tentatively place the X27 state at ∼70 cm−1 above the ground X7 state.