Stark-width measurements of neutral and singly ionized magnesium resonance lines in a wall-stabilized arc

Stark widths of the Mg I 2852.13-Å and of the Mg II 2795.53- and 2802.70-Å resonance lines have been measured in the ranges of electronic density and temperature 1.10-1.64×${10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$, 12 900-14 300 K. The light source is a stationary, optically thin, wall-stabilized arc burning in argon with a small addition of Mg vapor. Plasma parameters are measured with the use of line and continuum radiation of the argon plasma. Optical depth measurements are performed at the peaks of the investigated lines, and the Mg concentration is continuously controlled to minimize the reabsorption. High spectral resolution is achieved by use of a piezoelectric scanned Fabry-Pérot interferometer whose instrumental profile is measured and found to be Voigt shaped. The experimental profiles are analyzed using a least-squares fit of the Voigt function to all profile intensity points. The Stark width of the Mg I resonance line is found to be 30 to 50% lower than the existing semiclassical calculations. No quantum calculations and no other experimental values are available. As to the Mg II resonance doublet, its width is found lower by a factor of 2 than all the previous experimental values but those of Roberts and Barnard, and our value agrees well with the full quantum calculations of Barnes.