Theoretical prediction of a carrier gas effect under nucleation in thermal diffusion chambers

Abstract

Analytical dependencies of critical supersaturation S * and ∂ S */∂ P on a carrier gas pressure P 0 and temperature T in a diffusion cloud chamber (DCC) are derived on the basis of the microscopic nucleation theory [A.L. Itkin, E.G. Kolesnichenko, Microscopic Theory of Condensation in Gases and Plasma, World Scientific, New York, 1997], specially modified for the case of diffusion-limited nucleation [A. Itkin, Kinetic model of effect of a carrier gas on nucleation in diffusion chamber, Aerosol Sci. Technol., in press], and a proper treatment of transport processes in a DCC. These dependencies qualitatively reproduce available experimental data. In addition, an effect of nature of both the carrier gas and condensing vapor on the observed phenomenon is discussed. The conclusion is made that the effect of the carrier gas in the experiments in a DCC has no connection to the real rate of chemical reactions of clusterization and, at other conditions (for instance, in expansion chambers), may not occur. Nevertheless, an existence of the carrier gas influence on the total nucleation rate can be of great importance for the control of nucleation.