Specific absorption spectra of cerium in multicomponent silicate glasses

Photoionization of glass requires photon energies larger than the bandgap of the glass matrix. To shift the photosensitivity of a glass to longer wavelengths, it is common to add a sensitizer, e.g. cerium. Cerium has two valence states but only the Ce3+ is UV-photoactive. Hence, we present a spectral method that allows determining specific absorption spectra of both valent states of cerium in two different silicate glasses. Two overlapped absorption spectra, one for Ce3+ and one for Ce4+, were observed in soda lime silicate glass. It was found that both spectra consist from two Gaussian bands. Specific absorption of each ion was calculated on the basis of balance equations written for glasses melted under different redox conditions and used to estimate the absolute concentration of each ion. An identical analysis was performed on a photosensitive multicomponent silicate glass (photo-thermo-refractive (PTR) glass). It was found that absorption band of Ce3+ in PTR glass is shifted to short wavelength region due to the presence of fluorine while absorption spectra of Ce4+ are identical. The effect of UV-exposure on absorption spectra of cerium was studied. An absorption spectrum of photo-ionized Ce3+ is not identical to that of Ce4+: UV-exposure induces a new band resulting from Ce3++ and electron color centers.