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.