Questions Concerning the Stopping Power of Heavy Ions in Solids

Abstract

The passage of heavy ions through solid targets is a topic which continues to puzzle investigators in various aspects. Historically, the problem was specifically treated first by Bohr [1] and Bohr and Lindhard [2]. Since that time, much progress in understanding has been achieved for both slow and fast collisions [3–5]. One of the remaining difficulties arises from the fact that the high spatial density of foil target atoms causes a high rate of electronic collisions which, due to the formation of copious excited states, cannot be treated independently. To circumvent this problem, successful theories of energy loss treat the target on the basis of an extended electron gas [3]. Despite the remarkable advantage for handling of atomic collision processes in this manner, we emphasize that a basic lack of understanding of the particular situation in solid targets still exists especially for heavy ions in certain velocity ranges. This situation is illustrated below.