Diffraction of atoms from stepped surfaces: A semiclassical chaotic S-matrix study.

The diffraction of atoms from stepped surfaces is treated using the semiclassical S-matrix theory. Two different regimes of the behavior of the classical trajectories, regular and chaotic, are considered. For the latter case, the diffraction order function presents a fractal structure, and there is an infinite number of trajectories connecting the initial and final states. Using the scaling laws of the fractal, within the formalism of the S-matrix theory, we have obtained diffraction and specular intensities, which are in fairly good agreement with the experimental and quantum close-coupling results. @S0163-1829~96!00221-4#