MULTIPLE-SCATTERING SUPPRESSION IN DILUTE AND CONCENTRATED                     COLLOIDAL DISPERSIONS

                                                                             SEGRE PN, PUSEY PN
                           NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA D-CONDENSED MATTER ATOMIC
                                        MOLECULAR AND CHEMICAL PHYSICS FLUIDS PLASMAS BIOPHYSICS
                                                                   16: (8) 1181-1191 AUG 1994
 

                                                                                     Abstract:
We describe the design and operation of an improved two-colour dynamic light scattering (TCDLS) equipment
which effectively suppresses multiple scattering and allows the study of the Brownian dynamics of optically turbid
samples. The technique operates by cross correlating scattered light of two different colours. With the appropriate
scattering geometry, only singly scattered light contributes to the time-dependent part of the measured intensity
cross-correlation function thus allowing straightforward interpretation of the data. To test the performance of the
instrument we have studied several dilute colloidal suspensions, which, although dilute enough that free diffusion
of the particles can be assumed, ranged from quite transparent to distinctly turbid. We have confirmed that the
measured cross-correlation functions accurately reflect only single scattering even in the presence of strong
multiple scattering. As a first application of the technique, we have performed light scattering measurements on
concentrated suspensions of PMMA particles in cis-decalin.