Energy loss of light ions in diamond

The energy loss of 2-12 MeV protons, 12-18 MeV alpha particles and 24 MeV lithium-7 ions transmitted through thin (4-18 μm) diamond crystals has been measured for random incidence and for incidence along the [110], [111] and [100] axial channels. The ratio of channelled to random stopping is found to be the same for all three ions at the same velocity. The ratio of the stopping power at the leading edge of the channelled peak to random, taken as a measure of the ratio for best-channelled particles is found to be 0.64 +- 0.02 for the [110] axis for 12 MeV protons. The results are compared with several recent theories of channelled energy loss and are found to lie between the predictions of Dettmann and Esbensen and Golovchenko. A theoretical approach using a spatially periodic dielectric function is found to give results close to those of Esbensen and Golovchenko. (orig.)