ABSTRACT
The origin of scattering experiments has its roots in the development of modern atomic theory at the beginning of this century. As a result of both the Rutherford experiment on the scattering of alpha particles (He nuclei) by thin metallic foils and the Bohr theory of atomic structure, a consistent model of the atom as a small massive nucleus surrounded by a large swarm of light electrons was confirmed. Following these developments, it was realized that the inverse process, namely, analysis of the scattering pattern of ions from crystals, could provide information on composition and structure. This analysis is straightforward because the kinematics of energetic atomic collisions is accurately described by classical mechanics. Such scattering occurs as a result of the mutual Coulomb repulsion between the colliding atomic cores, that is, the nucleus plus core electrons. The scattered primary atom loses some of its energy to the target atom. The latter, in turn, recoils into a forward direction. The final energies of the scattered and recoiled atoms and the directions of their trajectories are determined by the masses of the pair of atoms involved and the closeness of the collision. By analysis of these final energies and angular distributions of the scattered and recoiled atoms, the elemental composition and structure of the surface can be deciphered.
