  Diffraction patterns produced by grazing scattering of fast atoms from
insulator surfaces are used to examine the atom-surface interaction. The method
is applied to He atoms colliding with a LiF(001) surface along axial
crystallographic channels. The projectile-surface potential is obtained from an
accurate DFT calculation, which includes polarization and surface relaxation.
For the description of the collision process we employ the surface eikonal
approximation, which takes into account quantum interference between different
projectile paths. The dependence of projectile spectra on the parallel and
perpendicular incident energies is experimentally and theoretically analyzed,
determining the range of applicability of the proposed model.
