Fiscal Year 1998 report theoretical studies of ground energy coupling

Abstract

A method for calculating the redistribution of resonance radiation in hot, dense plasmas is developed by extending the Frequency Fluctuation Model (FFM). This paper is devoted to a brief review of lineshape theory in the linear response approximation, and an introduction to the FFM approach to the modeling of lineshapes in plasmas. This discussion begins with a consideration of the spectral lines emitted by complex ions in plasmas. As is well known, the lineshape is determined by the time- dependent coupling of the ion with the plasma environment. This plasma-emitter interaction, leads to Stark broadening of the spectral lines, and traditionally has been considered in the approximation which treats the effect of the electrons on the emitting ion in the impact limit while the ionic perturbation is taken to be quasi-static. In this approximation, the time dependence of the perturbation has been eliminated, resulting in a spectral line shape that has purely homogeneous and inhomogeneous contributions and that is described by a simple sum of independent electron impact broadened static components. In order to clarify the concepts presented, examples of radiative redistribution functions for simple cases are presented. Included is an example of an X-ray laser pumped system which illustratesmore » the capability of the mpdel to provide a sensitive method for the study of radiative transfer under plasma conditions of partial redistribution. That is, in cases where the strong mixing limit is not attained so that the mixing of the inhomogeneous spectral line components is not fast enough to produce a completely redistributed line.« less