ABSTRACT: The usefulness of photon correlation spectroscopy (PCS) for the determination of particle size in colloidal suspensions is well established. Most PCS experiments measure the time correlation function of polarized scattered light. However, if the scattered light is depolarizad, dynamic and structural information on the dispersed particles can be made available, which is difficult to obtain by other techniques. One of the reasons for the less frequent use of this technique is that the depolarized signal is orders of magnitude weaker than full signals, and hence more sensitive to experimental errors. Depolarized light scattering by monodisperse suspensions of ellipsoidal hematite (a-Fe2O3) particles was employed for the determination of the size (equivalent volume spherical diameter) and shape (axial ratio) of the particles. From the dependence of the decay constant of the photocount correlation function with the scattering angle, information on both quantities was obtained for ellipsoids with sizes between n 100 and 200 nm and axial ratios ranging from 0.19 to 0.59. Reasonable agreement was obtained with data deduced from transmision electron microscope pictures.

Keywords: Colloidal ellipsoids; depolarized light; dynamic light scattering.