Inhomogeneous width of oxygen-deficient centers induced by electron irradiation of silica

We report a study of the luminescence activity of oxygen-deficient centers stabilized in as-grown synthetic silica, as compared with the same defects induced by . irradiation at increasing doses, ranging from 1.2 x 103 to 5 x 106 kGy. We experimentally observe a progressive broadening of the luminescence band with increasing total electron dose released on samples. By analyzing our data within a theoretical model capable of separating homogeneous and inhomogeneous contribution to the total luminescence linewidth, we observe that the increasing of the width is entirely ascribable to the inhomogeneous component which increases, in the most irradiated sample, of 60% with respect to the value in the as-grown sample. This effect can be due either to the progressive creation of new defects statistically exploring different sites of the matrix, or to a progressive structural transformation of silica host which affects the optical properties of induced point defects.