Determination of Atom-Surface van der Waals Potentials from Transmission-Grating Diffraction Intensities

Molecular beams of rare gas atoms and ${\mathrm{D}}_2$ have been diffracted from 100-nm-period ${\mathrm{SiN}}_x$ transmission gratings. The relative intensities of the diffraction peaks out to the eighth order depend on the diffracting particle and are interpreted in terms of effective slit widths. These differences have been analyzed by a new theory which accounts for the long-range van der Waals ${-C}_3/l^3$ interaction of the particles with the walls of the grating bars. The values of the $C_3$ constant for two different gratings are in good agreement and the results exhibit the expected linear dependence on the dipole polarizability.