Low-frequency elastic behavior of a supercooled liquid

By X-ray photon correlation spectroscopy we quantify the influence of elasticity and viscosity on the capillary wave (CW) surface dynamics of a supercooled liquid. To fit the data a novel model combining Maxwell-Debye and Voigt-Kelvin viscoelasticity is derived yielding a saturation of relaxation rates at high q as well as an offset in the CW dispersion relation. Diffuse X-ray scattering confirms the result and data taken on the surface of supercooled polypropylene glycol (PPG-4000) evidence a low-frequency elastic plateau of the storage modulus. A possible connection between the observed solid-like response and the supercooled state is discussed. Copyright (C) EPLA, 2008.