Photoinduced anisotropic conversion of bonding and lone-pair electrons inAs2S3sglass

We present the results of a study of photoinduced anisotropy in a model chalcogenide glass ${\mathrm{As}}_2$ ${\mathrm{S}}_3$ in a wide spectral range using reflectance-difference spectroscopy. We have found that the anisotropy is induced at energies much exceeding the energy of the inducing photons and that the sign of the photoinduced anisotropy is opposite at smaller and higher energies. To explain the results, we suggest a model considering redistribution between bonding and lone-pair electrons.