Review of stopping powers in organic materials

Abstract

A survey of tests concerning Bragg's rule of stopping power additivity is updated, summarising recent evidence on chemical binding and physical state effects on stopping power in organic and related materials. A general failure of simple additivity is well-established, but magnitudes of effects are still subject to uncertainty. Phase effects in organic materials are ~ 5–10% at stopping power maximum for H and He ions, decreasing as energy increases. The stopping cross-sections of gases are greater than those of the equivalent condensed phase. Accuracy of stopping power measurements in organic compounds is often insufficient to unambiguously detect and quantify such effects. However sensitive tests of additivity can be obtained where uniform series of measurements have been carried out by one group with one method in a range of materials.