CHARGING OF AEROSOL IN THE TRANSITION REGIME

The present paper examines the ionic charging of small aerosol particles in the intermediate Knudsen regime. A numerical Monte Carlo algorithm has been developed and applied for the calculation of the ionic charging rate. In the vicinity of the particle, ion motion is modeled in the framework of classical Langevin scheme. In the intervals between the ion-neutral molecule collisions ion trajectories were calculated with allowance for electrostatic interaction between the ion and the particle. At distances from the particle surface larger than several ion mean free paths in the carrier gas, ion concentration distributions are found by solving continuum transport equations. A comparison between the experimental results and the data obtained by virtue of the described algorithm, as well as with the predictions of the Fuchs theory is presented. It is shown, that in the transition regime the dependence of dimensionless charging current on particle size can be described by simple empirical formula.