Experimental study and stochastic interpretation of oscillatory effects in backscattering spectra in planar channeling

Backscattering experiments with 1.9 MeV He ions were performed to study the oscillating trajectories of particles in planar channels of iron crystals. Strong maxima in planar aligned spectra are observed. Spectra registered for particles entering the crystal with angles of incidence with respect to the plane greater than the critical angle also exhibit strong maxima. Calculations which do not take into account multiple scattering predict qualitatively the experimental results. In order to obtain a quantitative agreement a stochastic model which accounts for the effects of multiple scattering is proposed and yields very good fits to the experimental results. (U.S.)