How would react ion of some gas (low energy anion or cation) in vicinity of a grounded metal surface or in vicinity of an insulator? I guess a free electron and cation would automaticly recombine. But I don't know the probability nor mechanisms (just tunneling?) for the same thing happening with a cation and a grounded electrode. When it ends up like an electrolysis (the atom will stuck on the electrode) and is there a way to prevent that? Anions are another thing. I guess that voltage slope around the electrode (induced by anion itself) wouldn't be sufficient to 'pluck' the electron away from the anion. Sorry for dumb questions.