ABSTRACT
The charging process of particles by gaseous ions depends on two physical mechanisms: fi eld and diffusion charging. When ions drift along electric fi eld lines and impinge on the particle, the charging process is referred to as fi eld charging. Diffusion charging is due to thermal collisions between particles and ions. Photoelectron charging, in which electrons are emitted from particles by UV irradiation, is also used to control the particle charge.
