  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 nearly a hundred new Fe I level identifications. Thirty-nine
LS levels are identified largely by incorporating published 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 mutual 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 over 16,000 of its potentially
detectable lines with theoretical gf values. For over 2,000 of these, this work
also includes astrophysical gf values, ones adjusted semi-empirically to fit
the stellar spectra. The potential impact of this work on modeling UV and IR
stellar spectra is noted.
