van der Waals forces between objects covered with a chromium layer

Abstract

Dispersion forces between two metal objects have been measured at distances varying from 132 to 670 nm. Precautions had to be taken to eliminate electrostatic forces arising from differences in Volta potential. The distance between the metallic objects was determined by measurring the capacitance formed by the test objects. To compare experiment and theory van der Waals forces between chromium objects have been calculated numerically on the basis of the Lifshitz theory. It is shown that when the dielectric constant of chromium is described by the free electron gas model and when an absorption band is taken into account excellent agreement with experiment is obtained. In addition the validity of a number of approximate equations for calculating the force is tested.