Extension of a Simple Model for f-d Transition and Applications to Reassignment of Excitation Spectra of Ho³⁺-Doped Crystals

We present an extension of the original simple model for f--d transition proposed by Duan and co-workers Phys. Rev. B 66(2002)155108; J. Alloys Compound. 366(2004)34 to the case applicable to heavy lanthanide and actinide ions in crystals and apply it to the interpretation of the low-temperature f--d excitation spectra of Ho³⁺ doped in crystals LiYF₄ and CaF₂. A consistent assignment of all the transition bands is obtained.