Plasma balls? Are those the 6 inch glass spheres with the plasma discharge things? Had one once and it burned out. The light you see is from recombination. Electrons knocked off molecules recombine emitting the light you see.
Is it correct to say that part of the light this lamp produces comes from the sequence:
1) atom gets ionized
2) electron accelerates (its ion too, of course)
3) collision between accelerated electrons and atoms (or ions)
4) atom (or ion) gets excited with this collision
5) atom (or ion) relaxes emitting photon.