Radial Profile of the Spectral Width of the Ar 7 d [5/2]3–4 p [3/2]2 Line inside the Cathode Fall Region of Ar Hollow Cathode Discharges

The spatial variation of the spectral width of the Ar 7d[5/2]3–4p[3/2]2 transition inside the cathode fall region of hollow cathode discharges was examined by laser optogalvanic spectroscopy at various discharge currents and gas pressures. A close yet complicated correlation with the spatial distribution of the electric field was found to be present, and attempts were made to acquire and summarize qualitative understanding of the observation. The spectral width at the cathode surface, Δω_c (in cm⁻¹), was found to be related to the corresponding Stark shift, Δν_c (in cm⁻¹), by Δω_c = (0.0021 ± 0.0002)Δν_c in cm⁻¹.