interest in a search of hypothetical fields beyond the standard model [@Ono06].

In the experiments the dispersive forces are usually measured between a sphere and a plate. In the vdW regime the force depends on distance $d$ as $A_H R/6d^2$, where $R$ is the radius of the sphere. Fits of the experimental data yielded an effective Hamaker constant $A_H\approx (7-25)\times 10^{-20}\;J$ for gold-water-gold systems [@Ton91]. On the other hand, for $Au$-air-$Au$ surfaces studies by Tonckt et al. [@Ton91] using the surface force apparatus in the plane-sphere geometry with millimeter size spheres yielded an effective Hamaker constant of $A_H\approx 28\times 10^{-20}\;J$ for separations $d>8.5\;nm$. Similar values $A_H\approx 29\times
10^{-20}\;J$ [@Pal08] were obtained from AFM force measurements at separations between $12\;nm$ - $17\;nm$. We are using here the term “effective Hamaker constant” because in this distance range the van der Waals asymptotic regime is not fully reached. Fitting the curve force vs distance following from the Lifshitz theory in the range $d=1-5\;nm$ one would find the Hamaker constant to be $A_H\approx 40\times 10^{-20}\;J$ as it is expected between metal surfaces [@But05]. However, in this distance range the experimental determination of the constant for $Au$-air-$Au$ is problematic due to the strong influence of 