Interaction of Slow Electrons with Insulating Crystals. I. Absorption Coefficient for Cleaved Alkali Halides; Experimental Techniques

Abstract

Techniques have been developed that will permit a unique determination of an absorption coefficient δa for 0.2- to 20-ev electrons on cleaved, insulating crystals. Two classes of electron trapping levels, one that empties rapidly and one that does not empty at room temperature, may exist in the target and if they do, effects caused by them may perturb the data. Experimental techniques were developed to compensate for each characteristic effect. Pure and nonstoichiometric KBr and KCl crystals were studied. The probability that a crystal-incident electron results in a charge influx was found to vary makedly as a function of the impact energy and in a manner characteristic of the target. This feasibility study indicates that slow electron beams could be a powerful tool for diagnosing surface and bulk properties of insulating crystals.