Optical absorption of Eu 3+ and Eu 2+ in europium oxides and europium fluorides

Optical absorption of Eu3+ and Eu2+ ions in the polycrystalline europium oxides and fluorides was studied by the diffuse reflectance spectroscopy method. For all europium compounds, characteristic narrow peaks of 4f-4f electron transitions are observe. Their positions are rather independent upon the type of a compound. However, their intensity and number significantly vary, especially from the transition oxides to fluorides. In addition to those, shoulders of fundamental absorption in the oxide Rd- spectra of the oxide materials arise. Substitution of Eu2+ ions for Eu3+ ions in the EuF3 - lattice causes a sharp change of the spectral characteristics. It is accompanied by an appearance of the wide band due to 4f-5d-electron transitions.