  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
about 10 % the plasma wavelength 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 AH 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.
