Charge transfer shake-up satellites in X-ray photoelectron spectra of cations and anions of SrTiO₃, TiO₂ and Sc₂O₃

Satellite structures have been observed at 12, 19 and 30 eV below the main peaks in the X-ray photoelectron spectra of the Ti, Sr and O levels of BrTiO₃. It is shown that these satellites are attributable to monopole charge transfer shake-up transitions (O 2pe_g → Ti 3de_g, O 2pa_1g → Ti 4sa_1g, and O 2se_g → Ti 3de_g, respectively). Charge transfer shake-up satellites have also been observed in the cations and anions of TiO₂ and Sc₂O₃. The first observation of shake-up satellites in the anion levels of these oxides with a 3d⁰ configuration is additional evidence to support the interpretation that shake-up satellites in transition-metal compounds arise from monopole charge transfer transitions. In general, the first shake-up satellite occurring on the high binding energy side of the transition-metal compounds can be attributed to 2pe_g → 3de_g monopole charge transfer transitions because the probability of the first allowed shake-up, 2pt_2g → 3dt_2g, is very low.