I'm a little confused as to what reactions are considered ionizations. Is there any requirement for the educts, for example?
Some references suggest that it's only considered an ionization if you produce additional charged atoms/molecules from the educts (and some processes are dubbed detachment, which intuitively look like ionizations to me). Then "double ionization" wouldn't be possible, strictly speaking. To what extend have electrons to be produced. At the moment I think that it's legal to call most processes that look like ionization ionization.
There is a remark in the wikipedia article regarding the distiction from dissociation, but I don't really understand it.