Correlations between hydrodynamic and intermolecular interactions

Abstract

Dynamic light scattering can be used to measure the intensity autocorrelation function. The limiting initial slope (the first cumulant) is susceptible to variation due to hydrodynamic and intermolecular interactions. The first cumulant of the intermediate scattering function is calculated for several interaction potentials with hydrodynamic interaction in the Oseen approximation. Solutions of the Percus–Yevick equation provide the required radial distribution functions for the equations derived by Ackerson and Felderhof. Spherically symmetric particles are considered at volume fractions of 0.0262 to 0.10. Corrections to the first cumulant are found to be as large as 40%. The model potentials were chosen to probe the dependence of the hydrodynamic interaction effect on the details of the interaction potential. This study represents an effort to explore such effects on the measured first cumulant. Qualitative agreement is found for experimental results. Some qualitative features of the solute–solute interactions can be determined from comparisons of measured and calculated hydrodynamic effects of several model potentials.