Site-dependent luminescence of Cu+ ions in silica glass

Absorption and luminescence spectra for interconfigurational 3d10 ↔3d94s transitions of Cu+ ions in a glass of near-pure silica have been studied. The observed dual luminescence characteristics (≈ 433 and ≈ 490 nm) and their excitation dependence have been ascribed to two different Cu+ ion sites in the glass. Correlation of the two excitation spectra with the absorption spectrum allowed us to identify the oxygen coordination of the individual sites as tetragonal (≈ 490 nm) and cubic (≈ 433 nm) in behavior. The long lifetime and bi-exponential behaviour of each emitting state indicated that the emitting states are triplets (3Eg, 3T2g) each of which is split by spin-orbit interactions.