Stark profiles of some ion lines of alkaline earth elements

The widths and shifts of Mg⁺, Ca⁺, Sr⁺ and Ba⁺ lines broadened by electron and ion Stark effects have been measured in an argon welding type plasma. The electron density is about 1.3×10¹⁷ cm^-3 and the temperature is about 13,000°K. Special care was taken to avoid self-absorption of resonance lines. Injection of alkaline earth elements into the cold region of the plasma edge permitted reliable measurements of the signs of line-shifts. Experimental results are compared with semi-classical theories and a new-classical computation of Sahal-Bréchot in which resonances of elastic cross sections are taken into account. Good agreement is observed between experiment and the later calculations.