The kinetics of colour centre formation in quartz

Abstract

It is shown that when free carriers are generated in a solid containing two or more types of defect capable of trapping electrons or holes, the occupancy of one type of trap is not, in general, a simple irradiation time dependent function of the form 1-exp (-t/τ) but is dependent on the parameters of the other traps and at saturation can be significantly lees than unity. Using a model for crystalline quartz it is possible to explain radiation bleaching by both x-rays and neutrons, by considering the dependence of the occupancy of one trap on other traps. With the same model an explanation of the effect of heat treatment on the kinetics of colouration observed by Forman (1961) is given. From a quantitative comparison between the predicted and observed rate curves of an x-ray irradiated crystal, f-values and defect concentration are calculated. Less detailed comments are made on the coloration of fused quartz.