Effects of Dielectronic Satellite Broadening on the Emission Spectra From Hot Plasmas

Abstract

We recently presented1 a model for the computation of spectral lines in hot plasmas based on the intermediate coupling scheme. In order to obtain meaningful photoabsorption cross-sections from which emission spectra can be calculated, the spectral lines must be endowed with realistic line-shape functions. In our present model we include the Doppler, electron Impact and quasi-static ion-Stark broadening mechanisms in the computation of the line profiles. Assuming statistical independence for the above broadening processes, the resulting profiles are computed by convolution of the individual line-shape functions. In addition, we investigate the modification of the spectral profiles by the presence or absence of shifts caused by spectator electrons occupying high Rydberg levels. When a spectator electron is close to the radiating electron, the dielectronic satellite line Is well separated from the principal line. On the other hand, a spectator electron in a high n level causes only a minor shift, and a distribution of spectator electrons over the high n levels causes an additional broadening of the lines that we call “dielectronic satellite broadening” (DSB). If the plasma is in local thermodynamic equilibrium (LTE), we assume that the average population p. of a single- electron level ∊ i is given by the Fermi statistics $$ {{\rm{p}}_{\rm{i}}} = {{\rm{w}}_{\rm{i}}}/\{ \exp [{ \in _{\rm{i}}} - \mu /{\rm{kT}}] + 1\} $$ (1) where wi, µ and kT stand for the statistical weight of the level ∊ i, the Fermi level and the temperature of the plasma, respectively.