Ion–ion plasmas and double layer formation in weakly collisional electronegative discharges

Plasmas of electronegative gases often separate into two distinct regions: an ion–ion core and an electron–ion periphery. Under certain conditions, a double layer may form at the boundary between the two regions. In weakly collisional three-component electronegative plasmas, formation of a double layer depends on the ratio of the electron to negative ion temperatures, and the ratio of the electron to positive ion densities.