Photolytic Darkening and Electronic Range in AgCl

Abstract

Photolytic darkening and electron range were investigated for a series of silver chloride crystals cut from a single boule which was grown in vacuum by the Bridgman technique. The effect of annealing atmosphere on both the initial darkening rate and electron range is discussed. Darkening produced by absorption of light in the tail of the fundamental band is shown to have a volume and a surface component. The volume darkening produced in a vacuum-annealed crystal is capable of absorbing but not scattering light. The darkened crystal can be bleached selectively with high efficiency by exposure to light near the peak of the induced absorption band. Difficulty is found with interpreting the results entirely in terms of a classical theory for light absorption by colloidal particles suspended in a dielectric medium. Crystals annealed in air darken quite differently then vacuum-annealed samples and crystals heated in chlorine show little sensitivity to light. Somewhat smaller but regular differences in low-temperature electron range were found for the various crystals heat treated in different annealing atmospheres.