Sign of the Casimir-Polder interaction between atoms and oil-water interfaces: Subtle dependence on dielectric properties

TL;DR

This study reveals that Casimir-Polder interactions between noble gas atoms in water and oil-water interfaces are highly dependent on the specific dielectric properties of the oil, showing both attraction and repulsion depending on the oil type and distance.

Contribution

It demonstrates the surface-specific nature of Casimir-Polder energies at oil-water interfaces, highlighting the subtle dependence on dielectric properties and the transition from repulsive to attractive forces with distance.

Findings

Interactions vary significantly with oil type.

Repulsive interactions dominate at short distances, becoming attractive at larger distances.

Surface-specific effects may influence biological processes.

Abstract

We demonstrate that Casimir-Polder energies between noble gas atoms (dissolved in water) and oil-water interfaces are highly surface specific. Both repulsion (e.g. hexane) and attraction (e.g. glycerine and cyclodecane) is found with different oils. For several intermediate oils (e.g. hexadecane, decane, and cyclohexane) both attraction and repulsion can be found in the same system. Near these oil-water interfaces the interaction is repulsive in the non-retarded limit and turns attractive at larger distances as retardation becomes important. These highly surface specific interactions may have a role to play in biological systems where the surface may be more or less accessible to dissolved atoms.