On the use of Ar I 517.753 nm spectral line for electric field measurements in the cathode sheath of a Grimm-type glow discharge source

Abstract

We present the results of the optical emission spectroscopy study of the Ar I 517.753 nm spectral line, observed at different positions in the cathode sheath of an abnormal DC Grimm-type glow discharge source operated in argon. The line profiles were recorded parallel to the cathode surface (side-on view), along the discharge axis from the cathode towards the negative glow. The spectra show a red line shift, which diminishes with the distance from the cathode surface and decreasing electric field. This allows experimental determination of the coefficient C in quadratic relation, Δν = CE2, between the wavenumber Stark shifts, Δν, and electric field strength, E. The above relation is a low-field (up to 25 kV/cm) approximation of the quadratic dependence of the upper-level shift, measured for a large set of argon lines at high electric fields (up to 700 kV/cm) by Windholz (Phys Scr 21:67–74, 1980). One of these lines, Ar I 537.349 nm, is used here for independent measurement of the electric field E and correlated with the Ar I 517.753 nm upper-level wavenumber shift Δν to obtain a line-specific coefficient C. In this way, the Ar I 517.753 nm spectral line complements the set of argon lines suitable for Stark spectroscopy diagnostics of the electric field distribution and cathode sheath length, the knowledge of which allows for a better understanding and description of the glow discharge processes through various theoretical models. Graphical abstract: [Figure not available: see fulltext.].