Nucleation: Measurements, theory, and atmospheric applications

New experiments have succeeded in measuring actual rates of nucleation and are revealing the shortcomings of classical nucleation theory, which assumes that the molecular-scale regions of the new phase may be treated using bulk thermodynamics and planar surface free energies. In response to these developments, new theories have been developed that incorporate information about molecular interactions in a more realistic fashion. This article reviews recent experimental and theoretical advances in the study of nucleation of liquids from the vapor and of crystals from the melt, with particular emphasis on phenomena that relate to particle formation in the atmosphere.