Effects Seen in the Passage of Positively Charged Ions through Single Crystals

This paper reports on some effects seen when swift, positively charged light ions are passed through various monocrystalline materials. The main part of the work concerns blocking effects observed when protons in the energy range 3-12 MeV were passed through thin (∼10 mg/${\mathrm{cm}}^2$) monocrystals of silicon. The energies and spatial distributions of the emergent particles were recorded both with photographic plates and with an automated scanning detector. In addition to the usual distribution of particles produced by Rutherford scattering, the spatial distributions are observed to include sharp lines corresponding to the planes of the target crystal. The observed widths of these lines are found to vary inversely as the square root of the energy of the incident ion. A calculation which traced the paths of ions through a hypothetical rigid lattice gave results qualitatively in agreement with observation. Photographic plates exposed to protons from the reaction ${\mathrm{Si}}^{28}\mathrm{}(d,p)\mathrm{}{\mathrm{Si}}^{29}$ occurring in a silicon crystal showed blocking phenomena similar to those observed with elastically scattered protons. In the angular region in which scattering is changing to blocking, the intensities of particles show a behavior that could be the result of wave phenomena.