Similarity treatment of phase effects in stopping power for low energy heavy charged particles

Abstract

Bragg's additivity rule is the basis for calculating stopping powers of compounds from data on their constituent elements. Major assumptions in applying it are that chemical binding and the physical state of the stopping material have negligible influence on the slowing down process. The fragmentary and, at times, conflicting evidence for phase effects for low energy heavy charged particles is summarised. A detailed survey of published stopping powers has been made and the information grouped according to target medium and phase. Each group has been fitted to universal curves of Lindhard type with the object of separating phase contributions to stopping. Least square fits have been made to each set of data. From these a quantitative measure of the effect is obtained and presented as stopping power ratios (vapour/condensed phase).