Takashi OKAMOTO and Toshimitsu ASAKURA

Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido, 060 Japan

(Accepted August 22, 1994)

The cross-correlation properties of dichromatic light multiply-scattered by colloidal particles in a uniform flow are studied experimentally. It is shown that the correlation peak value of intensity fluctuations depends on the optical thickness of the sample and the number density of particles, whereas the decay time of cross-correlation functions is almost independent of the characteristics of particle suspensions. This result indicates that the number fluctuations as well as the speckle fluctuations contribute to the temporal variations in the intensity, and that the velocity of the uniform flow is measurable without being affected by the diffusive motion of the scatterers. The effect of wavelength difference is also examined.

Key words : multiple scattering, dynamic light scattering, speckle, spectral correlation, colloidal particles, Brownian motion, velocimetry