Diffraction intensities in helium scattering; topographic curves

Diffracted beam intensities have been calculated using the hard corrugated wall potential and the so-called GR method, for numerous values of the corrugation parameter and incident angle. Curves of equal intensity are drawn as a function of these two parameters (topographic curves). They give a clear description of diffraction phenomena. Comparing to experimental data, the potential corrugation is determined for alkali halide, for dense metallic surfaces and tentatively for tungsten (112) face. So the microscopic roughness seems to be the parameter which can explain the quite different behaviour of these surfaces regarding the scattering of helium. The potential corrugation of the repulsive part of the potential is discussed in terms of localization of delocalization of electrons in the vicinity of atom cores. (Auth.)