Study of ion dynamic effects at low electron densities on the lines He I 447.1 and 492.2 nm

Abstract

The effects of ion motion on the Stark profiles of the lines He I 447.15 nm (2 3P-4 3D) and its forbidden component He I 447.0 nm (2 3P-4 3F) has been studied in a plasma jet for electron densities between 0.8 × 10 21 and 4 × 10 21 m -3. The ion velocity was changed by using perturbing ions of different masses. An important smearing of the central part of the line was observed, and there was some evidence of an extra-broadening of the line when the ion velocity increased. A comparison of our results with the recent Model Microfield Method calculations shows an improved agreement in the line profile description relatively to previous calculations. A confirmation of these measurements was given by the study of the ion motion effect on the profile of the line He I 492.19 nm (2 1P-4 1D) and its forbidden component He I 492.03 nm (2 1P-4 1F).