Dispersion forces between fused silica objects at distances between 25 and 350 nm

Abstract

Direct measurements of dispersion forces between a fused silica lens and a fused silica flat plate were carried out for a range of separations between 25 and 350 nm. At separations greater than 50 nm, retarded dispersion forces were observed, while at shorter distances a transition towards unretarded dispersion forces was detected. The value of the retarded Hamaker constant for fused silica was 1.05 × 10^–19 erg cm, about twice the value predicted by the Lifshitz theory.