Observation of a phenomenon of UV-light-induced photo-oxidation of copper(I) under doped conditions in a silica glass has been reported and a mechanism of electron transfer from the photo-excited precursor (Cu +)* to a neighbouring ionized aluminium centre [AlO 4Na +] + which is also generated in the glass as a result of UV irradiation has been proposed. Calculation of the metal—ligand interaction parameters of the photo-produced Cu 2+, revealed that the oxygens surrounding the majority of the ions in the glass have a square planar coordination structure where the ligands form a strong covalent bond with the cation.