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

We report x-ray reflectivity measurements of liquid mercury between -36 °C and +25 °C. The surface structure can be described by a layered density profile convolved with a thermal roughness ${\sigma }_T.$ The layering has a spacing of 2.72 Å and an exponential decay length of 5.0 Å. Surprisingly, ${\sigma }_T$ is found to increase considerably faster with temperature than the $\sqrt{T}$ behavior predicted by capillary wave theory, in contrast with previous measurements on Ga and dielectric liquids.