Thermal energy atomic scattering on solid surfaces (TEAS) provides information about the very top layer of the solid surfaces, because the probe particles (usually He atoms) do not penetrate into the surface. The problem is the following: does the scattering probe particle feel a two-dimensional surface lattice? Is the kinematic theory right? If the probe particle does not penetrate into the surface too deep the particle experiences a plane with the lattice atoms. If the probability of penetration into deeper layers is not negligible the Bragg diffraction peaks are shifted.
A computer model simulation has been chosen to investigate the diffraction pattern. The physical model contains a wave-packet that describes the atomic beam and a pair-wise interaction potential that characterizes the solid surface [1][2]. During the computations the wave-packet is scattered on the solid surface and the directions of the diffraction peaks at the detector region are compared with the results of Bragg condition. The method requires the numerical solution of time dependent Schrödinger equation. The above described method refines the theory of diffractive peaks in case of the TEAS.
 

[1] G. Varga, Applied Surface Science, (1999) vol.144-145 p. 64-68.
[2] G. Varga, Surface Science, (1999) vol. 441 p. 472-478.