A very fast method to account for charged particle dynamics effects in calculations of spectral line shape emitted by plasmas is presented. This method is based on a formulation of the frequency fluctuation model (FFM), which provides an expression of the dynamic line shape as a functional of the static distribution of frequencies. Thus, the main numerical work rests on the calculation of the quasistatic Stark profile. This method for taking into account ion dynamics allows a very fast and accurate calculation of Stark broadening of atomic hydrogen high- n series emission lines. It is not limited to hydrogen spectra. Results on helium- beta and Lyman- alpha lines emitted by argon in microballoon implosion experiment conditions compared with experimental data and simulation results are also presented. The present approach reduces the computer time by more than 2 orders of magnitude as compared with the original FFM with an improvement of the calculation precision, and it opens broad possibilities for its application in spectral line-shape codes.

A new channel for recombination of free electrons on multicharged ions with a complex core is under investigation. The channel is connected with a dynamic polarization of an ion's core by the colliding electron which results in radiation of the core and capture of the electron. This new channel (called polarization recombination, PlR) is estimated in the frame of a statistical (Thomas-Fermi) model of the complex ion. It is shown that the contribution of PlR to the total recombination rates may be comparable to or exceed (by more than an order of magnitude) the standard contribution of radiative recombination.

We consider the effects of plasmas on dielectronic-recombination ͑DR͒ rates. Effects of plasmas electric fields on DR rates are analyzed in detail in the space of parabolic quantum numbers. A quasiclassical approach is used to obtain general analytical expressions for DR rates in the parabolic basis for arbitrary types of ions having transitions without change of core principal quantum numbers (⌬nϭ0 transitions͒ responsible for the main contribution to DR rates. The approach makes it possible to investigate scaling laws for dependences of both total and differential DR rates on atomic parameters. Effects of electron collisions and ionization are taken into account with the help of cutoff procedures. Numerical data are presented for Li-and Na-like ions under typical plasma conditions. A comparison with numerical calculations for specific ions is presented.

A polarization recombination channel of electron on heavy ions with a complex core is under investigation. The channel is connected with a dynamic polarization of an ion's core which results in radiation of the core and an inelastic transition of electron. This channel is estimated in the frame of statistical model of the complex ion. It is shown that the contribution of polarization radiation may be comparable or exceed the standard radiation contribution. The signi¢cance of interference e¡ects is demonstrated as well.# Physica Scripta 1999Physica Scripta T80

A universal approach for the calculation of Rydberg atom line shapes in plasmas is developed. This approach goes far beyond the calculation capabilities of the standard models. It is based on analytical formulae for the intensity distribution in radiation transitions n − n′ between highly excited atomic states with large values of principal quantum numbers n, n′ ≫ 1, with Δn = n − n′ ≪ n, and on the frequency fluctuation model to account for ion thermal motion effects. The theory allows us to describe a transition from the static to the impact broadening domains for every hydrogen spectral line. The specific cases of broadening of Hn−α(Δn = 1) and Hn−β(Δn = 2) lines are considered in detail for various values of plasma parameters. The line shapes are presented in a universal manner as functions of the relative frequency splitting and of the fluctuation rate ν of the ion plasma microfield, using dimensionless variables. For small values of ν, the static line shapes which generalize the well-known Underhill–Waddell data for the Rydberg state case are presented. For large values of ν, the transition to impact ion broadening is observed, resulting in a narrowing effect. A comparison with the hydrogen Hα line shape calculations shows a good agreement between the universal approach for Rydberg lines and traditional spectral line shapes.