RADIOLUMINESCENCE IN AMORPHOUS SILICA - TEMPERATURE-DEPENDENCE AND RELAXATION

Radioluminescence measurements on preform and fiber amorphous silica s pecimens have been made in the temperature interval 6 to 300 K and wav elength regime 300 to 800 nm. A typical spectrum consists of peaks at similar to 550 (main band) and similar to 650 (secondary band) nm, whi ch are associated with self-trapped excitons and nonbridging oxygen ho le centers of the silica lattice, respectively. Radioluminescence from the main band decays with increasing temperature and becomes undetect able in the 130 to 170 K range, consistent with the decay of self-trap ped holes. Assuming the decrease in radioluminescence with temperature to be due to quenching of self-trapped exciton radiative recombinatio n, with a spread in quenching barrier energy, we derive an expression of the form L(T)=L(0)/[1 + AT + BT2 + CT3], which yields an excellent fit to the experimental data. An observed time-dependent relaxation of radioluminescence is associated with the enhancement of nonradiative recombination. (C) 1998 Elsevier Science B.V. All rights reserved.