Lognormal size distributions in particle growth processes without coagulation

A new model is proposed to explain lognormal particle size distributions found in vapor growth processes such as gas evaporation, without invoking coagulation. In the model, particles are moving by diffusion and drift through a finite growth region. The particle size is assumed to be a power function of growth time, and the final size distribution is determined by the first passage times. By computer simulation, lognormal size distributions and scaling laws interrelating the distribution parameters, the size of the growth region, and the drift speed were found.