Ion bombardment of alkali halides, III: Track-effect analysis of measured damage profiles in KCl

Single crystals of KCl were bombarded with monoenergetic beams of protons (1.5 MeV and 2.3 MeV) and alphas (2.3 MeV). Fluences varied from 1012 to 1014 cm−2. Combining the results of a photomicrographic procedure with values of crystal optical density, profiles yielding F centers/cm3 versus depth were obtained. It is observed that F-center concentration does not follow dE/dx. Profile shapes and magnitudes are accounted for in terms of the established concept of an ion infratrack, characterized by high energy density and dose rate, surrounded by a region of low energy density. The latter is assumed to have an F-center production efficiency characteristic of electron beam irradiation. The infratrack is found to have a significantly higher efficiency and to dominate F-center production. Analysis of data indicates that infratrack efficiency versus velocity may be independent of the identity of the incident particle, and leads to predictions regarding anticipated F-center production by heavy ions.