Knowledge Bank

The velocity modulation lineshapes and velocities of ions in the positive column of AC glow discharges have been studied with difference frequency and diode lasers. The lineshape study was based on the mathematical model proposed by Solka $et.al.1$ The 2f signals of a variety of ions were used to examine this model. The evolution of lineshape with phase is the result of ion lifetime, modulation frequency, and the effective duration of the discharge current. From the splitting of the 2f signal, with known effective electric field in the positive column, it is possible to derive ion mobility directly. The axial and radial electric fields (or ion velocities) in the positive column were found to be of the same magnitude, which is in agreement with the result reported by Ganguly and $Garscadden.2$