LOCAL DYNAMIC PROPERTIES OF VITREOUS SILICA PROBED BY PHOTOLUMINESCENCE SPECTROSCOPY IN THE TEMPERATURE-RANGE 300-4.5 K

We report experimental data on the thermal dependence, from room tempe rature to 4.5 K, of the photoluminescence activity in the spectral reg ion between 4.0 and 4.5 eV, for different types of vitreous silica. Th e three photoluminescence bands previously detected in this energy ran ge, alpha(E), alpha(I) and alpha(R), are investigated by analyzing the temperature dependence of their spectral moments. This method enables us to obtain information on both the electronic properties of the chr omophores responsible for the observed emissions and on the structural and dynamic properties of their environment. Our results show that di fferent point defects present different coupling constants with their surroundings and that the pristine properties of the silica samples is relevant in determining the structural heterogeneity and the mean fre quencies of the vibrational modes that couple with the electronic tran sition. (C) 1998 Elsevier Science B.V. All rights reserved.