Ion-Aerosol Attachment Coefficients and the Diffusional Charging of Aerosols

Abstract

The relative importance of image capture and three-body trapping in calculating the ion-aerosol attachment coefficients for aerosol particles of small radii is evaluated. The results show that for uncharged nuclei the image capture sphere is always larger than the trapping distance and therefore the trapping distance plays no role in the attachment of ions to uncharged particles. However, for singly (doubly) charged particles with radii below about 2 × 10^-8 (5 × 10^-8) m the trapping distance is larger than the image capture distance, and therefore must be included in ion-aerosol attachment theories for small aerosol particles. Calculations of the combination coefficients including both the effects of image capture and three-body trapping are presented and compared to experimentally determined values.