Surface light scattering: a methodological review

Abstract

The methods used in the application of light scattering to the study of thermally excited capillary waves on liquid surface or interfaces are reviewed. The focus is on the use of photon correlation to determine the spectroscopic information carried by the scattered light. Particular attention is directed to extraction of the maximum amount of information from the data, including surface viscoelastic parameters and intensities.

Surface and Bulk Elasticity Determined Fluctuation Regimes in Smectic Membranes

“…Irakli Sikharulidze, 1 Bela Farago, 2 Igor P. Dolbnya, 3 Anders Madsen, 4 and Wim H. We report combined x-ray photon correlation spectroscopy (XPCS) and neutron spin echo (NSE) measurements of the layer-displacement fluctuations in smectic liquid-crystal membranes in the range from 10 ns to 10 s. NSE reveals a new regime, determined by bulk elasticity, in which relaxation times decrease with the wave vector of the fluctuations. XPCS probes slower surface-tension-dominated relaxation times, independent of the wave vector.…”

“…XPCS gives a difference in correlation times at specular and off-specular positions that can be related to different detection schemes. Low-dimensional ordering and the associated fluctuation behavior are of considerable general interest and have been studied for a wide variety of systems comprising smectic membranes (freestanding smectic films), Langmuir films, Newtonian black films, and surfactant and lipid membranes [1,2]. In this context, smectic membranes provide unique, substrate-free, and almost perfectly oriented model systems [1].…”

“…For NSE measurements at the spectrometer IN15 of the Institute Laue-Langevin (ILL, Grenoble, France) [10], membranes of 50 50 mm 2 were stretched on an aluminum frame. These large-size membranes were not of uniform thickness; instead, several different regions were observed with a thickness from about half a micron at the top of the frame up to a few microns at the bottom.…”

Effects of partial coherence on correlation functions measured by x-ray photon correlation spectroscopy

“…5,6 Previous experiments with optical photon correlation spectroscopy techniques, known as dynamical light scattering ͑DLS͒, have been used to investigate various fluid systems. 14,15 However for DLS measurements of lowviscosity liquids the experimentally determined damping constants ͑viscosities͒ were greater than those obtained by conventional techniques. This issue was first addressed and explained by Langevin. 14, 16 The effect was related to broadening ͑resolution͒ effects of the experimental setup.…”

Effect of viscosity on dispersion of capillary–gravity waves

“…The dispersion of capillary waves has been studied mostly by photon correlation spectroscopy [3][4][5][6][7]. The experimental technique analyzes line broadening of scattered light from thermally excited capillary waves to infer dispersion and attenuation data [8][9][10][11][12].…”