New optical centers of triply charged cerium ions in silica gel-glasses saturated with hydrogen

The influence of annealing in hydrogen on spectral-luminescent properties of Ce-containing silica gel-glasses vitrified in air at 1200 degrees C has been investigated. It is established that such annealing at temperatures from 1000 degrees C to 1200 degrees C for highly activated glasses is accompanied by the formation of two main types of new luminescent optical centers of triply charged cerium ions. These centers differ from the centers obtained at lower annealing temperature by positions of the Sd-sublevels and by higher optical transition probabilities. The formation of these new centers is due to the structural reorganization of Ce-containing clusters. Such reorganization is explained by the relaxation of the local environment of reduced (Ce4+)(-) ions incorporated into the clusters to the equilibrium state. (C) 1999 Elsevier Science B.V. All rights reserved.