Identification of Fe⁴⁺ and Fe⁵⁺ charge-transfer photochromic absorption bands in SrTiO₃

Optical absorption and the enhancement and bleaching of Fe3+ and Fe5+ electron paramagnetic resonance in SrTiO3: Al measured as a function of wavelength and time show that the photochromic absorption bands are due to electron transfer from O2- valence states to Fe4+ and Fe5+. They occur at 2.09 and 2.82 eV for Fe4+ and at 1.99 and 2.53 eV for Fe5+. © 1975.