A study of the contribution of doubly excited ionic states to the properties of hot dense high-Z plasmas

The role of two-electron processes, i.e. dielectronic recombination and autoionization, in the ionization balance and X-ray emission of hot dense plasmas composed of various high-Z materials is explored. Tungsten, gold, lead and uranium are considered. It is shown that the average ion charge and the high-energy emissivity are both sensitive to the dielectronic recombination rate. A systematic study demonstrates the degree of this sensitivity. It is found that the complete neglect of these 2-electron processes introduces a large error but once included, the key physical properties are quite insensitive to the rate over the important 2–3 keV temperature range. The high-energy emissivity depends strongly on temperature, peaking at conditions corresponding to a closed shell system, and on the square of the electron density, as for a coronal system.