Effect of iron ionization balance on X-ray spectral analysis

Wehave investigated the uncertainty in the ionization and recombination rates for iron and its impact on the derivation of the iron elemental abundance fromX-ray emission spectra. Most uncertainty is found in the dielectronic recombination rates for iron ions with L-shell outer electrons. The quantitative effect of this uncertainty on the derivation of the iron abundance depends on the spectral resolving power of X-ray detectors. With the resolution achieved by ASCA, the differences among ionization balance models come out to ∼30% in the iron elemental abundance and∼15% in the temperature at temperatures kT ∼ 1 keV. To eliminate the effects of the ionization balance, finally, we suggest taking ionization temperature as well as the electron temperature into account for spectral analysis. Thisway is useful also for plasmas in the presence of ionizing photons.