Mechanisms of Photochemical Reactions of Europium Ions in Aqueous Acid Solutions

Published data on photochemical reactions of Eu(II), Eu(III) ions in aqueous solutions wereconsidered. Previously proposed mechanisms of these reactions are unlikely. We suggest that photoexcited Euion forms with the unexcited ion a dimer (so-called excimer), which decomposes with liberation of H₂ and two Eu(III) ions in the case of Eu(II) oxidation and with liberation of H₂O₂ and two Eu(II) ions in Eu(III) reduction.