X-ray reflectivity study of temperature-dependent surface layering in liquid Hg

We report x-ray reflectivity measurements of liquid mercury between {minus}36thinsp{degree}C and +25thinsp{degree}C. The surface structure can be described by a layered density profile convolved with a thermal roughness {sigma}{sub T}. The layering has a spacing of 2.72 {Angstrom} and an exponential decay length of 5.0 {Angstrom}. Surprisingly, {sigma}{sub T} is found to increase considerably faster with temperature than the {radical} (T) behavior predicted by capillary wave theory, in contrast with previous measurements on Ga and dielectric liquids. {copyright} {ital 1998} {ital The American Physical Society}