Argon clusters and homogeneous nucleation: Comparison of experiment and theory

Abstract

Free energies for the formation of atomic microclusters of Lennard-Jones argon are computed. All interactions are considered in the calculation of the force-constant matrix for the vibrational analysis. Introduction of these results into the early kinetic formulation of the classical theory of nucleation yielded nucleation rates for states of realistic isentropic expansions. The calculations are compared with recent Rayleigh light scattering experiments on homogeneous nucleation of argon in helium in steady supersonic nozzle flow. A steep rise of calculated nucleation rate at certain states in the expansion coincides with the observed location of the onset of condensation and remarkable agreement of experiment and theory is found. Further comparisons of the experiments with predictions obtained with the classical theory are not successful. As expected in an extreme situation of small clusters, no agreement of the liquid drop model with experiment can be obtained in a wide range of assumed material properties.