Radiation Induced Coloring of Glasses Measured during and after Electron Irradiation

The growth of color centers during irradiation, and the decay after irradiation, has been studied in two glasses using recently developed equipment for making optical absorption and luminescence measurements during and after electron irradiation. The glasses studied were NBS 710, a soda-lime silicate glass and NBS 711, a lead-silicate glass. Both glasses exhibit similar coloring characteristics. The radiation induced absorption spectra consists of a weak Gaussian shaped band in the visible, a stronger Gaussian band in the ultra violet and a band edge "shift" which may be accurately approximated by a third Gaussian band. For all absorption bands the color center vs. dose (or irradiation time) curves can be accurately resolved into two saturating exponential and one linear component. The decay curves obtained after the irradiation is terminated can be accurately expressed by three exponential components. Coloring and decay curves made at different dose rates indicate that the processes responsible for decay after irradiation and electron hole recombination during irradiation play important roles in determining the rate and extent of coloring. The results are qualitatively in agreement with some very simple kinetic treatments for color center formation. In some, but not all, respects the quantitative agreement is also good.