van der Waals forces between a Cs atom or a CsCl molecule and metal or dielectric surfaces

The interaction protentials between a spherically symmetric atom (Cs) and a highly conducting surface (gold) or a dielectric surface (glass) are investigated by the atomic-beam-deflection technique. The observed beam profile is least-squares fitted to an r^-3 potential. The derived interaction constant for the gold surface is 0.59 and 0.67 of the values predicted by Bardeen and Mavroyannis, respectively. A glass surface is found to have an interaction constant 0.65 that of gold. The measurements have also been obtained for a polar molecule (CsCl). With a gold surface the observed beam profile is almost identical to that for stainless steel (reported earlier) in spite of their difference in dc conductivity. Further, the observed constant for an insulator (glass surface) is 0.86 that of gold. With gold, the interaction constant obtained for a cesium-halide molecule, with a strong permanent dipole moment, is smaller than that for a Cs atom with zero dipole moment.