Stark broadening of the overlapping 4471.48 Å HeI line in a plasma. II. Nonmarkovian and ion dynamic effects

Abstract

The inclusion of a frequency-dependent collision operator in the line shape expression is investigated quantitatively for the 4471 Å overlapping HeI line. We compare at several electron densities frequency-independent (markovian) profiles with frequency-dependent (nonmarkovian) profiles taking into account incomplete electron-atom collisions. No significant discrepancies appear in the domain of validity of the impact approximations (| Δω| ⩽ ωp e ), whereas for the far wings important differences may be found. At the extrema (two peaks, one dip) the nonmarkovian intensities prove to be the higher ones. For a modest electron density, the inclusion of ion dynamic shielding introduces more modifications then nonmarkovian effects. In the blue wing, the frequency-dependent profile lies below the frequency-independant profile in accord with the hydrogenic behavior for that part of the line shape in the presence of a large perturber density.