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Thanks, the writing alone on that other one was atrocious.

Precisely ! Fe XXV ? That sounds a bit like descendent from a long line of monarchs.

NASA site spells it the same. Presumably it's how physicists call ions.

I learned to spell ions like that in highschool, though never more than Fe III, I think.

I also thought that FE XXV was a misspelling, or bad use of notation. But it's (apparently) the usual notation in spectroscopy. http://www.nist.gov/data/PDFfiles/jpcrd200.pdf

FE I is not ionized Fe (26 protons, 26 electrons, 0 net charge)

FE II is ionized Fe (26 protons, 25 electrons, +1 net charge)

FE III is not ionized Fe (26 protons, 24 electrons, +2 net charge)

...

FE XXV has (26 protons, 2 electrons, +24 net charge)

FE XXVI has (26 protons, 1 electron, +25 net charge)

--

This is not the standard chemical notation. In chemistry:

FE II is ionized Fe++ (26 protons, 24 electrons, +2 net charge)

FE III is ionized Fe+++ (26 protons, 23 electrons, +3 net charge)