We describe necessary and sufficient conditions for image transformations so that surfaces refracting or reflecting collimated beams exist. The surfaces are given by explicit formulas. When these conditions are not satisfied, ...

The influence of the collimating conditions of the incident beam on diffraction patterns produced by grazing scattering of fast atoms off crystal surfaces is studied within a semiquantum approach, called the surface initial ...

Diffraction patterns produced by fast He atoms grazingly impinging on a LiF(001) surface are investigated focusing on the influence of the beam collimation. Single- and double-slit collimating devices situated in front of ...