ABSTRACT
The charging process of particles by gaseous ions depends on two physical mechanisms: field and diffusion charging. Photoelectron charging, in which electrons are emitted from particles by UV irradiation, is also used to control the particle charge. Effects of the radicals and excited molecules on the particle materials should be considered when the ions are used to control the electrical charge. The physical properties of ions depend on the ion–molecule reaction and ion-clustering processes. Diffusion charging is caused by the kinetic energy of an ion and the electrostatic energy between a particle and an ion in the absence of an external electric field. Electrons in the solid are first optically excited into states of high energy; then they move to the surface of the solid and escape into the vacuum or gas phase. In order to control surface charge in liquid, an important approach is chemical surface treatment and modification.
