1986 Volume 19 Issue 3 Pages 214-221
The diffusion charging of ultrafine aerosol particles by bipolar ions, where positive and negative ion concentrations were unequal, was studied experimentally in a low electric field. Monodisperse particles with diameters from 20 nm to 60 nm were charged by unequal concentrations of bipolar ions having various number ratios of negative ions to positive ions, and were enlarged by condensation of DBF vapor on them for visualization. Positively charged particles were distinguished from negatively charged ones by observation of their behavior in the electric field. The experimental results on the charge distribution were found to depend on the number ratio of negative ions to positive ions and the product of total ion number concentration and charging time. Further, they were well described by the birth-death equation with the combination probability of ions and particles proposed by Fuchs.
