Gwyneth C. Junkel

Plasma Induced Line Shifts: New Light on an Old Controversy

It appears that the theoretical lines shifted according to calculations provide substantially better fits than the theoretical line shapes which exclude line shifts. The differing principal quantum numbers associated with the Ly-β and He-γ lead to significantly differing shifts. Thus, the use of unshifted lines, shifted arbitrarily, en masse, would not lead to the same quality of fit observed when using the lineshapes shifted according to calculation.

Plasma induced line shifts and their effects on line merging and population kinetics

Plasma-induced line shifts to the red have been observed in a number of laser-produced plasmas. After briefly reviewing some of the more recent of these observations and a method of calculating their magnitude, two implications of the existence of these shifts are explored. Firstly, calculations show for plasma conditions such as those in the reviewed experiments the redshifts are larger for lines originating from manifolds with higher principle quantum numbers. This leads to line merging at lower densities than would be expected without considering shifts. Secondly, even though the observed shifts are small with respect to kTe they can have a substantial effect on population kinetics calculations for loosely bound states which approximate the effects of continuum lowering on level populations through the use of effective statistical weights.