Cross-correlation intensity fluctuation spectroscopy applied to colloidal suspensions

Abstract

The method of cross-correlation intensity fluctuation spectroscopy (CCIFS) is presented and contrasted with other scattering techniques. While standard scattering techniques monitor structure factors which are related to particle pair correlation functions, the CCIFS technique is sensitive to higher-order correlation functions and may be used to monitor the local particle order in condensed phases. To demonstrate the CCIFS technique, cross-correlation data for scattering from a two-dimensional colloidal monolayer is presented. These cross-correlation data indicate a local hexagonal structure in the fluid phase. A model calculation is presented which treats the two-dimensional colloidal fluid phase as a randomly oriented hexagonal solid with large lattice vibrations. The results of this calculation are in qualitative agreement with experimental observation.