Dechannelling of 2 MeV He+ at a circular Frank dislocation loop in gold

The dechannelling cross section of a circular Frank dislocation loop of radius 19 Å, and of Burgers vector (a/3)(111) in gold crystal is calculated for (001) channeling of 2 MeV He⁺. The calculated value σ_c = 210 ± 10 Ų is satisfactory compared with the experimental value σ_e = 235 Ų by Merkel et al.     

On the coherent electronic excitation of channelled He+ ions

Emission of light from He⁺ ions transmitted though [111] axis of thin single crystal of gold has been studied and no effect of coherent electronic excitation could be detected.     

Diffusion models of dechannelling of energetic H+-ions in single crystals

The Fokker-Planck equations is shown to be a good expression to describe the dechannelling of energetic H⁺-ions in single crystals. The relation between the Fokker-Planck equation, the ordinary diffusion equation and the steady state model is discussed.     

Energy loss of scattered ions at glancing-angle incidence on the crystal surface

Experimental findings of glancing-angle scattering of energetic ions are reviewed with particular emphasis on the energy loss of ion during scattering. The position-dependent stopping power of the surface which is derived from the angular dependence of observed energy loss is explained in terms of single and distance electron excitations of surface electrons. For the ions with velocities less than the Fermi velocity of target valence electrons, it is shown that the stopping power of a surface is determined only by the elastic collisions of the ion with valence electrons. From the analysis of the energy losses of 12–30 keV He ions reflected from the (001) surface of SnTe, a method is proposed to derive the electron density distribution averaged over the plane parallel to the surface from this position-dependent stopping power.     

Convoy electrons produced at glancing angle scattering of MeV HeH+ ions from a crystal surface

Abstract

Convoy electrons produced at glancing angle scattering of MeV HeH⁺ ions from an atomically clean (001) surface of SnTe crystal are observed. Energy spectrum of the convoy electrons shows a peak broader than that at scattering of atomic projectiles and the most probable energy of convoy electrons at HeH⁺ scattering is larger than those at scattering of isotachic He ions. This acceleration of convoy electrons is qualitatively explained by the force due to surface wake induced by Coulomb exploding fragment He²⁺ and H⁺.     

Direct scattering of channelling He ions at dislocations

The effects of misfit dislocations in epitaxial PbS/PbSe bi-crystals on the channeling of energetic He ions were studied. The direct scattering of channelling ions at dislocations was detected and its dependence on the energy of the incident ions was measured.