Measurements of the Casimir-Lifshitz force in fluids: the effect of electrostatic forces and Debye screening

摘要

In this work, we present detailed measurements of the Casimir-Lifshitz forcebetween two gold surfaces (a sphere and a plate) immersed in ethanol and studythe effect of residual electrostatic forces, which are dominated by staticfields within the apparatus and can be reduced with proper shielding.Electrostatic forces are further reduced by Debye screening through theaddition of salt ions to the liquid. Additionally, the salt leads to areduction of the Casimir-Lifshitz force by screening the zero-frequencycontribution to the force; however, the effect is small between gold surfacesat the measured separations and within experimental error. An improvedcalibration procedure is described and compared to previous methods. Finally,the experimental results are compared to Lifshitz's theory and found to beconsistent for the materials used in the experiment.