Surface Roughness of Water Measured by X-Ray Reflectivity

Abstract

The roughness of the liquid-vapor interface for pure water was measured by a technique of x-ray reflectivity. With synchrotron radiation \((\lambda \sim1.5 \mathring{A})\), the angular dependence of the x-ray reflectivity was measured from grazing incidence \((\sim 0.0021 rad)\), where the reflectivity was greater than 0.96, to an incident angle of \(\sim 0.05 rad\), where the reflectivity was \(\sim 7×10^{-8}\). A fit to the data by a theory with only one adjustable parameter obtains \(3.2 \mathring{A}\) for the root-mean-square roughness of the water surface.