Doppler Broadening of Helium Ion Lines in a Low Pressure Helium Arc

Abstract
Profiles of Spectral lines emitted from a plasma in a low pressure helium arc which has an electron temperature of about 105°K and an electron density of about 1014 cm-3 have been studied. The results show that the measured profile of HeII 4686 Å can be well explained by Doppler broadening if the fine structure is taken into account. The apparent half-widths of HeII 4686 Å and HeII 3203 Å are shown in a figure as a function of the Doppler half-width of a fine structure component. The profile of HeII 3203 Å is mainly formed by Doppler broadening but Stark effect contributes to it by a few percents.