Analysis of resonance transitions in x-ray spectra of electron interaction with highly charged iron ions

In electron interactions with highly charged Fe ions, the X-ray spectra were theoretically analysed and compared with the experimental results at the Tokyo EBIT. In the present analysis, cross sections for dielectronic recombination, resonance excitation, resonance recombination, and direct excitation were calculated by use of the distorted wave method. Simulated spectra were obtained by convoluting the calculated cross sections with the experimental beam energy resolution and X-ray detector resolution, which are in close agreement with the experimental observations. Based on our calculations including polarization effects, we estimate the charge state balance: He-like Fe24+ (74%), Li-like Fe23+ (18%), and Be-like Fe22+ (8%), and the ion density in the trap to be 6.5 - 8.5 x 108 cm-3. The present calculations were also compared with the previous high-resolution measurements of the KLL resonances in He-like Fe ions. (author)