Multiple scattering of channeled ions in crystals

Abstract

The Focker-Planck equation for scattering of channeled ions by electrons and thermal vibrations of crystalline lattice atoms has been obtained and solved. For calculations use is made of two models of the electron density distribution in a channel: the Thomas-Fermi model and the free-electron model. Axial and planar channeling is considered. It is shown that scattering by electrons plays an important part in ion dechanneling. In particular, in axial channeling scattering by electrons has a dominant effect on dechanneling of fast light ions. A comparison is made between theory and experiment on dechanneling of fast ions in tungsten and silicon.