Investigation of sol–gel silica samples with different Ge-doping content and with concentration of O-deficient centers less than 1016 centers/cm3 was carried out after γ-irradiation by electron paramagnetic resonance, optical absorption and photoluminescence measurements. It was found that in the dose range below 5kGy paramagnetic centers with the characteristic resonance line of Ge(1) defects were induced in all the investigated samples, whereas no signatures of other Ge related centers or E’-Si were detected. Optical measurements detect two absorption bands peaked at 4.5 and 5.8eV and no variation in the emission spectra of highly doped materials. From these results new suggestions arise for the correlation between the Ge(1) centers and the optical absorption bands at 4.5 and 5.8eV and for the absence of correlation of Ge(1) with Ge- O-deficient centers.

Ge-Related Centers Induced by Gamma Irradiation in Sol–Gel Ge-Doped Silica. S.Agnello, R.Boscaino, M.Cannas, F.M.Gelardi, F.La Mattina, S.Grandi, A.Magistris: Journal of Non-Crystalline Solids, 2003, 322[1-3], 134-8