Ar I and Ne I Spectral Line Shapes for an Abnormal Glow Discharge Diagnostics

We report the results of an Ar I and Ne I line shape study in an abnormal glow discharge operating in argon and neon. The spectral lines were observed along the axis of a cylindrical glow discharge parallel (side-on) and perpendicular (end-on) to the cathode surface. The side-on spectra show spectral line shifting and sometimes simultaneous shifting and splitting in the cathode fall region of the glow discharge. The results of the measured line shift with available data for the dc Stark effect are used for measurement of electric field strength in the cathode fall region of the glow discharge. Electron temperatures of 2860 K and 4770 K in the negative glow region of argon and neon discharges, respectively, were determined from the relative intensities of Ar I or Ne I lines using the Boltzmann plot technique. An electron number density of ≈1020 m−3 (±25%) in the negative glow region of the argon discharge was determined from the widths of two plasma-broadened Ar I lines using theoretical Stark broadening data. The end-on recorded line profiles show 10–40% larger half-widths than the side-on recorded line profiles from the negative glow. This effect is a result of the superposition of line emission in the cathode fall region under the influence of the dc Stark effect on the line profile from the negative glow.