Directional effects on the motion of swift ions in anisotropic media are studied. The stopping power is a function of the direction of the velocity relative to the principal axes of the medium, and there is a nonzero lateral force on the ion tending to bend its trajectory. These effects arise from the anisotropy of the dielectric response, and are distinct from channeling. Simple expressions are derived for the stopping power and lateral force in the nonrelativistic, high-velocity limit, and results are presented for crystalline graphite.

• Received 16 October 1989

DOI:https://doi.org/10.1103/PhysRevA.42.1390