Condensation of Water Vapor in a Cloud Chamber

摘要

The condensation of water vapor was investigated in a cloud chamber by measuring pressure as a function of time. -A dense mist reproducibly formed, suggesting homogeneous nucleation occur¬red in the present work. Nucleation at low temperature (230°K| was significantly faster than the 0. 4 particles/cc predicted by the classical theory of nucleation, and the classical theory therefore is suspect. The present results were compared to several models of condensation kinetics obtained by combining collision-frequency growth kinetics with the recent 10 revised nucleation theory amended for various types of monomer loss. Results faintly suggested that ultra 3 small water clusters are about 10" as stable as predicted by macroscopic cluster thermodynamics. Compression of the bulk gas due to heat conduc¬tion from the hot walls was appreciable, both during and after expansion. Previous work which appeared to support the classical nucleation theory probably is obscured by heat conduction during expansion.