A comparison of Kohler activation with nucleation for NaCl-H2O

The Kohler theory of activation is compared with classical nucleation theor y for the NaCl-H2O system. We find that for NaCl particles of the size typi cally found in the atmosphere the two processes are hardly distinguishable. Consequently, the usually preferred choice of simple activation theory ove r nucleation in the development and application of large scale atmospheric models, is reaffirmed. However, we also find that for small NaCl crystals c onsisting of 10-50 molecules, nucleation can occur at relative humidities s ignificantly lower than those required for activation. (C) 2000 American In stitute of Physics. [S0021-9606(00)50942-8].