Regular and statistical motion in a crystal at channeling. Evolution of the particle flux in a thick crystal

The analytic and simulation study of ion channeling in atomic string crystal results in significant revision of Lindhard statistical model. The modification consists in accounting for double channeling regime - the regular motion between atomic rows. The normal channeling, having a character of the random walk in the field of atomic string, admits the description in statistical frames which reflects the global instability of ion trajectories. It is shown that the focusing by pairs of atomic strings results in increased intensity of nuclear scattering and electron stopping of ions in an angular range essentially exceeding Lindhard angle. The lattice thermal vibrations result in intertransitions between the named above regimes; the double channeling plays a role of attractor in this diffusion. At large depths the rechanneling becomes important. Also the anisotropy in angular distributions, the star patterns, is a characteristic feature at these depths. The volume rechanneling is a cause of the super-tail appearance in an ion range distributions for random motion initial conditions