Abstract
The rich emission and absorption line spectra of Fe I may be used to extract crucial information on astrophysical plasmas, such as stellar metallicities. There is currently a lack, in quality and quantity, of accurate level-resolved effective electron-impact collision strengths and oscillator strengths for radiative transitions. Here, we discuss the challenges in obtaining an accurate model of the neutral iron atom and compare our theoretical fine-structure energy levels with observation for several increasingly large models. Radiative data is presented for several transitions for which the atomic data is accurately known.
Highlights
The extraction of information about plasmas from their spectra is made possible by accurate collisional-radiative modelling
We seek a description of the structure of the neutral iron atom and accurate values for the oscillator strengths for radiative transitions, defined by Hilborn [1], with the aim of calculating accurate Maxwell-averaged electron-impact collision strengths among the fine-structure levels of Fe I
To obtain oscillator strengths for radiative transitions and collision strengths for electron-impactexcitations, we required a suitable description of the neutral iron atom
Summary
The extraction of information about plasmas from their spectra is made possible by accurate collisional-radiative modelling. In terms of collisional data, the first and only set of R-matrix electron-impact excitation collision strengths was published in 2017 [4], albeit term-resolved rather than level-resolved This lack of radiative and collisional data for fine-structure transitions prevents us from fully exploiting the Fe I spectrum. The extraction of information from spectra on the abundance of neutral iron relies on the accurate population modelling of as many of its fine-structure levels as possible and, in particular, the availability of highly reliable oscillator strengths for many transitions. These are compared to experimental data, paying particular attention to the final model presented which is currently being used to generate a set of level-resolved collisional data for this species
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