AbstractAn analysis of the Ti K edge and Ta L edges yields that the chemical shift amounts to 0.8 eV by a valence charge increase. An exciton line is resolved like in other rutiles. Exciton binding energy amounts to 1.1 eV and decreases to 0.6 eV for high tantalum content. The coordination polyhedron size of titanium increases to 11 × 10−3nm with the tantalum content. This is essentially due to the increase of ionic radius of titanium by the valence charge increase. The crystal field splitting is found to be 3.1 eV for TiIV, 2.1 eV for TiIII, and (5.5 to 6.0) eV for TaV. It seems that the crystal field splitting is well correlated with the valence charge. Additionally a procedure is described to add several × absorption spectra recorded on several samples with the same composition but with different thicknes