Formation and properties of Na smoke particles

Abstract

The nucleation and growth of Na smoke particles were studied using light‐scattering techniques. Homogeneous nucleation occurred at a rate at least 10¹¹ slower than predicted by Becker‐Döring or Lothe‐Pound theory. This could be resolved either by assuming that the surface tension of small Na clusters (10 atoms) is larger than the bulk value or by applying a nucleation model which does not rely on macroscopic parameters. Particle growth initially occurred by single‐atom accretion and then by particle‐particle coagulation. Single‐atom accretion was found to have a significant effect on particle size in disagreement with the model of Granqvist and Buhrman. A coagulation constant for a 23‐nm‐radius Na particle was measured as 3.6×10⁻⁹ cm³/s and was found to be in agreement with the free‐molecular model of Fuchs.