Dechannelling model based on the stochastic theory for the axial channelling particles

The parameters in the Fokker-Planck equation to describe the depth dependence of fraction of channelling particles are calculated numerically from the scattering probabilities of axial channelling particles which suffer from the collisions with electrons and thermally vibrating chains of atoms. The fractions of channelling particles for high energy H+ and He++ ions are obtained by solving the Fokker-Planck equation and compared with the experimental data of axial dechannelling. It is shown from the numerical calculations that the Fokker-Planck equation is a good expression to describe the behaviour of axial channelling particles in single crystals. (author)