Rotational diffusion of colloid spheres in concentrated suspensions studied by deuteron NMR

We present a study of the application of deuteron-nuclear magnetic resonance spectroscopy (NMR) to the investigation of the rotational diffusion of spherical colloidal particles. We performed NMR pulse experiments on colloidal suspensions of polystyrene latex spheres In water-glycerol mixtures in a wide range of particle volume fractions phi from the dilute suspension up to phi=0.504. We have analyzed the stimulated echo NMR signal in the time domain. The full shape of the orientational correlation function deviates from an exponential behavior in the whole phi range examined. We evaluate the rotational diffusion;coefficient and calculate-its phi dependence up to the phi(2) term in view of the theory proposed recently [V. Degiorgio, R. Piazza, and R. B. Jones, Phys. Rev. E 52, 2707 (1995)], which considers the effect of two- and three-body hydrodynamic interactions upon particle reorientation. We find considerable slowing down of sphere reorientation for phi greater than or equal to 0.2. The agreement between experimental results and theoretical considerations is satisfactory.