Abstract

Line profiles of the plasma broadened lines He I: 3188, 3889, and 5016 Å and He II: 3203, 4686 Å have been determined from measurements using a wall-stabilized quasistationary pulsed discharge as a plasma source of sufficient homogeneity. The profiles were recorded applying the rapid-scan technique to enable single-shot registration of the spectral data. Electron density values were obtained from plasma-refractivity measurements at two different wavelengths using rare gas ion-lasers as background light-sources. The electron density range in this experiment was (0.7 -1.2) · 10¹⁷ cm⁻³. Temperature values of pure helium plasmas resulted from absolute radiation measurements (line intensities of He II 3203 Å and 4686 Å), yielding ~ 4 · 10⁴ K. In helium-hydrogen mixtures further used for plasma generation in the lower temperature region, temperature values could be estimated from the optically thick Balmer line H_α, yielding ~ 2 · 10⁴ K.

Experimental line shapes and half-widths are compared with the theoretical predictions of several authors and with the results of previous measurements. In case of neutral helium lines experimental and theoretical values agree within experimental accuracy (10%), whereas for the He II-lines the measured line shapes deviate considerably from the theoretical predictions.