Valence-band splitting of SrTiO3

Optical charge-transfer transitions from the oxygen valence bands to ${\mathrm{Fe}}^{5+}$ and ${\mathrm{V}}^{5+}$ impurity states at ${\mathrm{Ti}}^{4+}$ sites in SrTi${\mathrm{O}}_3$ reveal a 0.42-eV valence-band splitting. Since these transitions are observed with conventional optical-absorption spectroscopy, their resolution is far better than previously obtained by photoelectron spectroscopy.