On the dependence of a critical supersaturation on pressure of a two-component background gas in a diffusion cloud chamber

Abstract

An analytical dependence of a critical supersaturation S ∗ on partial pressures P i of a two-component (index i=1,2) background gas at a constant temperature in a diffusion cloud chamber (DCC) is obtained on the basis of a theory of diffusion-controlled nucleation proposed earlier by the author (J. Aerosol Sci., submitted). Despite this theory qualitatively and even quantitatively reproduces the available experimental data of Heist [1] a new experiment is proposed in order to examine it more carefully. For this purpose we imply to use a two-component mixture of insoluble gases as a background gas when performing a traditional experiment on studying the dependence of S ∗ on the background gas pressure in DCC. A new model of nucleation at such conditions is developed and it is shown that a variation of the pressures of both components of the two-component background gas in an appropriate way in DCC at a constant nucleation rate and the temperature in the maximum nucleation plane can result in both the increase and the decrease of critical supersaturation S ∗ and even keep S ∗ to be constant. This conclusion is the main result of the present theory which admits a direct experimental verification.