Structure of X-ray photoelectron spectra of lanthanide compounds

The results of the X-ray photoelectron spectroscopy studies of the electronic structures of trifluorides, oxides and other compounds of Sc, Y and lanthanides (Ln) from La to Lu, except for Pm, in the binding energy range from 0 to 1350 eV are generalised. The established dependences of the Ln4f binding energies and the relative intensities of lines on the atomic number Z do not contradict the theoretical data stating that the Ln4f atomic orbitals (AO) participate markedly in the formation of molecular orbitals (MO) in the lanthanide compounds. It is established that inner valence molecular orbitals (IVMO) composed of the metal Sc3p, Y4p, Ln5p AO and the ligand L(O,F)2s AO are formed in these systems in addition to the outer valence molecular orbitals (OVMO). It is shown that the spectral fine structure caused by multiplet splitting, many-body perturbation and dynamic effects is correlated with the lanthanide oxidation state, the spin state of ions and the mechanisms of the secondary electronic processes accompanying the photoemission and can serve as a characteristic for identification of lanthanide compounds. Charge induction is discussed using titanium and niobium double oxides as examples. The bibliography includes 206 references.