On the strengths of the Fourier components of gas-surface interaction potentials

Earlier calculations of the interaction potential energy of a gas atom with a solid, as a function of position of the gas atom [F. O. Goodman, Phys. Rev. 164, 1113 (1967)], are used to estimate the strengths of the Fourier components (in other words, the diffraction strengths) of gas-surface interaction potentials. The fcc(001) surface is discussed as it is relevant to the usual experiments involving LiF. Each Fourier component of potential is related to a reciprocal lattice vector of the surface, and it is concluded that the diffraction strengths decrease rapidly with increasing reciprocal lattice vector length. Essentially, at least for the purposes of calculations of diffracted intensities, the only nonnegligible diffraction strengths are those associated with the eight smallest nonzero reciprocal lattice vectors; the values of the nonnegligible diffraction strengths are estimated.