Effects of different doubly excited states on the ionization balance and M-emissivity in high-Z plasmas

Abstract

2-Electron processes play important roles in the ionization balance both in high and low temperature plasmas, so it is necessary to take into account doubly excited states in the population calculations, either explicitly or implicitly. In order to make clear what kinds of doubly excited states are most important, the effects of three types of doubly excited states on ionization balance and M-emissivity are investigated for gold plasmas within the condition of indirect drive experiments. The present results show that doubly excited states with an inner M-shell electron excited are most important. Omitting such states may decrease the ionization more than 10% and results in more than a magnitude lower M-emissivity. The reason is that including such doubly excited states enhances the ionization significantly while the enhancement in recombination is much weaker for charge states 37–48 when electron temperature is higher than 1.0 keV. We suggest that for gold, at temperature larger than 1.0 keV, M-shell excitation should be taken into account when ion charge is larger than 37. Effects on the ionization balance of the other two types of doubly excited states are not as strong as the one mentioned above, but the largest difference in M-emissivity would be 30% if neglecting one of the two types of doubly excited states with electron density no more than 1021 cm−3. At higher electron density (1022 cm−3), omitting triply excited states may decrease M-emissivity nearly 50% when temperature is around 1.0 keV.