ABSTRACT
This chapter discusses some experimental data on the solarization phenomenon for a number of common glass systems and exposure conditions. The use of x-rays can considerably enhance the solarization phenomenon because of the much higher number of electron/hole pairs that are produced. The self-trapping process requires strong electron-phonon interaction and the magnitude of the energy of the bandgap and additionally on structural disorder. The so-called traps are unoccupied energy levels near the conduction band and filled levels near the valence band. To explain the darkening and bleaching phenomena, the ultraviolet exposure wavelength must have sufficient energy to excite electrons into the conduction band. Electron spin resonance measures a broad spectrum of paramagnetic species. The bleaching occurs when the lectron gets into the conduction band, which can then recombine with the trapped hole. The suggested mechanism for the induced absorption is attributed to a charge transfer from the Fe+2 to Fe+3 with the electron being removed to the ligand.
