Excitons in SiO₂: a review

In this paper, excitonic properties of crystalline and glassy SiO₂ are reviewed. Experimental spectroscopic data (optical absorption and reflection spectra, as well as spectra of luminescence and its excitation), luminescence decay kinetics at different temperatures, and photoelectric properties - photoconductivity and photoelectron emission - were used to determine excitons in SiO₂. Information on migration of excitons was obtained on the basis of energy transport to impurity luminescence centers, the latter being detectors of quasiparticles. Determination of excitonic properties in glassy SiO₂ was based on the comparison of the observed phenomena in crystalline and glassy materials in approximately the same conditions. Structural peculiarities are analyzed comparing optical phenomena in crystalline α-quartz and cristobalite and in fused silica of four types. Models of excitons are based on propositions of chemical bond theory and total energy adiabatic potential.