Depolarized quasielastic light scattering from reaction limited aggregates of anisotropic spherical particles

Abstract

Reaction Limited Cluster Aggregation is a well known process showing universal features: i) aggregates are fractal with a fractal dimension d f ≅ 2.1, ii) the cluster mass distribution N(m) decays as m −τ for small m and exhibits a fast cut-off exp \(\left( {\frac{{ - m}}{{m_c }}} \right)\) at large m, and iii) m c grows exponentially in time. — In this work, we studied salt-induced aggregation of optically anisotropic spherical particles by quasielastic light scattering. By selecting the depolarized component at a low scattering angle we were able to collect only the rotational contributions to the field correlation function I VH . This greatly simplifies the data interpretation, leading to a correlation function which exhibits stretched exponential behavior. By measuring I VH at different aggregation time, we fully characterized the aggregation process by determining the fractal dimension, the cluster mass distribution and the aggregation kinetics in a single experiment. — Our results are in good agreement with previous experimental and theoretical works.Key wordsAggregationfractaldepolarized dynamic light scatteringoptical anisotropy