X-ray reflectivity study of an oil-water interface in equilibrium with a middle-phase microemulsion

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Abstract
The roughness and surface correlations of a surfactant monolayer at an oil-water interface in equilibrium with a small amount of middle-phase microemulsion were studied using x-ray scattering. High energy x rays in conjunction with tight instrumental resolution allow us to separate and quantify the specular reflectivity and surface diffuse scattering of the interface. The experimental results are explained using a height-height correlation function derived from a capillary wave model. The interface was found to have an intrinsic roughness of 85 Å and an interfacial tension of 0.11 dyn/cm.