Dynamics of hard sphere suspensions using dynamic light scattering and X-ray photon correlation spectroscopy: Dynamics and scaling of the intermediate scattering function

Abstract

Intermediate Scattering Functions (ISF's) are measured for colloidal hard sphere systems using both Dynamic Light Scattering (DLS) and X-ray Photon Correlation Spectroscopy (XPCS). We compare the techniques, and discuss the advantages and disadvantages of each. Both techniques agree in the overlapping range of scattering vectors. We investigate the scaling behaviour found by Segre and Pusey 1 but challenged by Lurio et al. 2 . We observe a scaling behaviour over several decades in time but not in the long time regime. Moreover, we do not observe long time diffusive regimes at scattering vectors away from the peak of the structure factor and so question the existence of a long time diffusion coefficients at these scattering vectors.

Particle sizing for flowing colloidal suspensions using flow-differential dynamic microscopy

“…a concentrated colloidal suspension, deviations from this simple exponential, due to particle interactions, are usually captured through a stretched exponential, f D = exp[−(q 2 Dτ) β ], with β < 1 the stretch exponent. 23 For very high concentrations, typical in colloidal glasses, the ISF may no longer decay to zero, suggesting the existence of 'fixed' particles that do not rearrange, often characterised by the non-ergodicity parameter. 23…”

Dramatic slowing of compositional relaxations in the approach to the glass transition for a bimodal colloidal suspension

“…Light scattering experiments are limited in the lowest wavevector that can be achieved (for an exception see Martinez et al [14]). Usually, the main interest is at the wavevector which corresponds to the structure factor peak.…”

“…However our attempt to include hydrodynamic interactions was only partially successful as the trend in the self di↵usion coe cients with packing fraction is qualitatively similar to that observed in Brownian dynamics simulations [13]. We calculated the intermediate scattering function (which is a key quantity measured in dynamic light scattering experiments [7,8,11,[14][15][16]) over a large range of packing fractions and wavevectors in order to systematically study the change in dynamics on the approach to the freezing point.…”

Electrokinetic and hydrodynamic properties of charged-particles systems

“…7 demonstrates that this relation is indeed valid to a decent approximation for charge-stabilized spheres. The validity of the time-wavenumber factorization scaling of S(q, t) has been repeatedly challenged, also for the reason that the true long-time regime can hardly be reached experimentally [113,114]). As it was argued already in [110], from a theoretical viewpoint dynamic scaling is merely an approximate feature.…”