He II, O III lines?

[Piano man]

Hi everyone,

I think this is a relatively straightforward question, but I can't find a simple answer for it on Google.
What do the Roman numerals stand for in He II and O III in relation to spectroscopy?

Thanks.

[Ken G]

He I is neutral, He II is once ionized, etc. A clunky notation, to be sure-- kind of like how 2011 is the "21st century."

[Piano man]

Thanks, that rings a bell alright - had a feeling it was something along those lines (no pun intended...) Cheers :D