The Debye-Waller factors and resonances in the diffraction of the atomic and molecular beams from solid surfaces are described.
The Debye temperatures determined by means of molecular beams are always larger than those obtained from LEED. These results are discussed qualitatively on the basis of the facts that the properties of the interactions of atoms and molecules with solid surfaces are considerably different from those of the interactions with solid surfaces.
The anomalous behavior of the diffraction intensities, which is called a resonance, has been found for many systems of molecules-solid surfaces. The intensity profiles in resonance are explained from the viewpoint of the standard scattering theory. Also it is emphasized that the interaction potentials of molecules with solid surfaces are determined by analysing only the resonance positions in the observed intensity curves.