http://arxiv.org/abs/2112.14742
The spectrum of neutral iron is critical to astrophysics, yet furnace laboratory experiments cannot reach many high-lying Fe I levels. Instead, Peterson & Kurucz (2015) and Peterson, Kurucz & Ayres (2017) turned to UV and optical spectra of warm stars to identify and assign energies for 124 Fe I levels with 1900 detectable Fe I lines, and to derive astrophysical gf-values for over a thousand of these. An energy value was assumed for each unknown Fe I level, and confirmed if it shifted the predicted positions in updated Kurucz (2011) Fe I calculations to match exactly in wavelength the positions of four or more unidentified lines in the observed spectra. Nearly all these identifications were for LS levels characterized by spin-orbit coupling, whose lines fall primarily at UV and optical wavelengths. This extension of these searches provides a hundred new Fe I level identifications. Forty LS levels are identified largely by incorporating the positions of unidentified laboratory Fe I lines with wavelengths < 2000A. Adding infrared spectra provided sixty Fe I jK levels, where a single isolated outer electron orbits a compact core. Their weak, blended lines fall mostly in the infrared, but are searchable because their neighboring energies obey tight relationships. For each new Fe I level, this work again provides and makes publicly available its identification, its energy, and a list of its lines with theoretical gf values. For suitably distinct lines, this work also includes astrophysical gf-values, ones adjusted semi-empirically to fit the stellar spectra.
R. Peterson and R. Kurucz
Thu, 30 Dec 21
28/71
Comments: 20 pages, 1 figure. Submitted to Astrophysical Journal Supplements. Table 3 of this submission is a stub table illustrating the form and content of the complete Table 3. This latter file is available online from that website upon its acceptance. It is also available from the website of R. Kurucz at this http URL
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