Caption: The Emission line spectrum of iron (Fe, Z=26).

Probably neutral iron (i.e., Fe I), but original caption is silent.

Is the spectrum real or simulated? Hard to tell these days, but yours truly guesses simulated.

Credit/Permission: User:SeeSchloss, before or circa 2006 / Public domain.
Image link: Wikipedia: File:Emission spectrum-Fe.png.
Local file: local link: line_spectrum_iron.html.
File: Spectra file: line_spectrum_iron.html.