Autoionization phenomena in plasma radiation processes

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Autoionizing resonances can play important roles in atomic radiation processes associated with electron-ion collisions in a high-temperature plasma. In the kinetic-theory description, autoionizing resonances provide indirect contributions to the rates for excitation, ionization, and recombination. Calculations have been performed for the rate coefficients describing dielectronic recombination, which is often the dominant recombination mechanism for non-hydrogenic ions. In the determination of the distribution of charge states, account has been taken of the contributions from autoionization following inner-shell-electron excitation and radiative stabilization following radiationless electron capture (dielectronic recombination). The radiative emission processes that have been investigated correspond to bound-bound, free-bound, and free-free transitions. Particular emphasis has been given to the detailed simulation of the K α satellite spectra due to both inner-shell-electron excitation and dielectronic recombination. In a sufficiently dense plasma, the populations of the autoionizing states can be substantially altered by both collision processes and plasma electric microfields. As a result, significant modifications can occur in the dielectronic recombination rates and satellite line intensities. It is desirable to treat these effects self-consistently with the high-density modifications to the spectral-line shapes, taking into account the same set of elementary atomic collision, radiation, and autoionization processes. A comprehensive framework for a self-consistent description is provided by a density-matrix approach, in conjunction with Liouville-space projection-operator and resolvent-operator techniques.