We present a study of argon glow discharge which shows that measured wavenumber DC Stark shifts Δν of two neutral argon lines, Ar I 518.75 nm and Ar I 522.127 nm, can be used for reliable determination of the electric field strength F distribution in the cathode sheath region of the discharge. In order to experimentally determine the coefficient c in quadratic correlation Δν = cF 2 , manifested in a low field range (up to 15 kV/cm), the discharge is seeded with a small admixture of hydrogen, and the values of F are measured via Stark polarization spectroscopy of the hydrogen Balmer beta line. Once known, this can be used for the determination of F by a simple and inexpensive spectroscopic Stark shift measurement in discharges with other argon admixtures or pure argon. Reported shift results are in good agreement with data extrapolated from measurements performed at high electric fields (over 100 kV/cm) by Windholz (Phys. Scr., 21 (1980) 67).
We present the results of an experimental study of Ar II line shapes emitted side-on from the cathode sheath (CS) region of an abnormal glow discharge operating in pure argon with different cathode materials. The shape of Ar II lines is recorded side-on to the discharge axis and parallel to the plane cathode surface by using the optical emission spectroscopy technique. Our experimental line shape analysis shows that the atomic line shapes can be used for determination of the electric field strength distribution and the thickness of the CS region, whereas the broadened wings of the Ar II lines provide an insight into line shape formation as a result of electric field strength distribution, which is essential for discharge particle dynamics, and interaction with the discharge gas and sputtered cathode material. The results are summarized in two analytic formulas: one for the half width of wings as a function of the cathode distance from the recording position and the other for correlation between Ar II line width and electric field strength.
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