Valence-alternation pairs as a possible cause of the unexpectedly strong fast relaxations in an oxide glass

Unexpected structural and dynamical features of non-crystalline As2O3, revealed through various light scattering techniques, indicate that this glass is distinctively different form other common oxide glasses. In view of its structural similarity with other chalcogenide glasses, i.e. As2S3 and As2Se3, it is suggested that the peculiar spectral properties of As2O3 may originate from structural configurations like those usually employed to account for photoinduced phenomena in chalcogenide glasses. The lone-pair electrons of oxygen atoms and the structural flexibility characterizing As2O3 compared to other tetrahedrally coordinated oxide glasses seems to be the key factor for the observed unique properties of this glass.