Dynamics of hard-sphere suspension using Dynamic Light Scattering and X-Ray Photon Correlation Spectroscopy: dynamics and scaling of the Intermediate Scattering Function

TL;DR

This study compares Dynamic Light Scattering and X-ray Photon Correlation Spectroscopy in measuring the Intermediate Scattering Function of colloidal hard spheres, examining their agreement, advantages, and the scaling behavior over time.

Contribution

It provides a comparative analysis of DLS and XPCS techniques and investigates the scaling behavior of the ISF in colloidal suspensions, challenging previous assumptions about long-time diffusion.

Findings

Both techniques agree in overlapping scattering vector ranges.

Scaling behavior observed over several decades in time, but not in the long time regime.

Long time diffusive regimes are not observed away from the structure factor peak.

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.