Transition from Casimir to van der Waals force between macroscopic bodies

The transition of van der Waals to Casimir forces between macroscopic gold surfaces is investigated by atomic force microscopy in the plane-sphere geometry. It was found that the transition appears to take place at separations similar to 10% the plasma wavelength lambda(p) for evaporated gold surfaces, which compares to theoretical predictions by incorporation of experimental optical data and roughness corrections. Moreover, the force data allow estimation of the Hamaker constant A(H) in the van der Waals regime, which is in good agreement with the Lifshitz theory predictions (even if roughness corrections are taken into account) and former surface force apparatus measurements. (C) 2008 American Institute of Physics.