Tracer Particle Diffusion in Crystal‐ and Fluid‐like Ordered Colloidal Suspensions

Static and dynamic light scattering experiments with crystal‐ and fluid‐like ordered colloidal suspensions are reported. The systems were composed of two electrostatically interacting particle species of similar size and effective particle charge but different refractive index. The refractive index of the abundant species was matched to the index of the dispersing medium. The incoherent scattering from the mismatched second species was used to investigate the self‐diffusion in the ordered suspension. Leakage of coherent scattering due to a slight mismatch was used to monitor simultaneously the structure factor S(Q) of the suspensions. – The self‐dynamic structure factor Fs(Q,t) at several ionic strength of the suspension is analyzed in terms of mean‐square displacements 〈R(t)2〉 and velocity autocorrelation functions v(0) v(t). The long time self‐diffusion coefficient is determined as a function of the effective hard sphere volume fraction Φ.