Luminescence bands in silica

Luminescence at 2.75 eV (450 nm) and at 4.4 eV (290 nm) is produced by excitation at wavelengths less than the band gap of silica (10 eV). Luminescence at these energies is also produced by excitation with x-rays, gamma rays, and energetic electrons and charged ions. A model has been proposed for the luminescence produced by energies less than the band gap energy. The differences in the amplitudes of the luminescence at 4.4 and 2.75 eV produced by photon energies greater than band gap and by 1 keV electrons provide the basis for proposing another center whose primary luminescence emission is at 2.75 eV and whose source is interstitial oxygen displaced by radiation with energies is greater than band gap energy (∼10eV).