  The optical conductivity ($\sigma_{1}$) of SrTiO$_{3}$ for various vacancies
has been systematically studied using a combination of ultraviolet - vacuum
ultraviolet (UV-VUV) reflectivity and spectroscopic ellipsometry. For cation
(Ti) vacancies, $\sigma_{1}$ shows large spectral weight transfer over a wide
range of energy from as high as 35 eV to as low as 0.5 eV and the presence of
mid-gap states, suggesting that strong correlations play an important role.
While for anion (O) vacancies $\sigma_{1}$ shows changes from 7.4 eV up to 35
eV. These unexpected results can be explained in terms of orbital
reconstruction.
