Electronic energy loss for helium channeling in silicon.

We present an analysis of the stopping power for helium in silicon taking into account the contributions due to different charge states. Our calculations include effects due to the nonuniformity of the target valence-electron density along specific crystallographic directions as well as the electron density of the projectile. In the present work attention is restricted to projectile velocities greater than or equal to the Bohr velocity in order to compare with existing experimental data. The method employs a dielectric-response formalism taken in the random-phase approximation coupled with energy-dependent population factors for the different charge states