Abstract

Dynamic light scattering studies of dense colloidal systems require special care due to problems of non-ergodicity and multiple scattering. We have combined a number of novel scattering techniques and developed a multi-speckle cross-correlation spectroscopy using a CCD chip as the detector. Cross correlation of pixels separated by a single scattering speckle length eliminates multiple scattering while averaging correlation functions from many speckles with approximately the same scattering wavevector performs the ensemble average. We use this technique to measure the phonons of a single hard sphere RHCP colloidal crystal which exhibits a well defined dispersion despite the complete anharmonicity of the interparticle potential.

© 2000 Optical Society of America