| Ion | Ionization potential | Ionization potential | Classification |
| lower (eV) | upper (eV) | ||
| O I | 0.0 | 13.6 | LIL |
| Al II | 5.9 | 18.8 | LIL |
| Si II | 8.1 | 16.3 | LIL |
| C II | 11.3 | 24.4 | LIL |
| Si III | 16.3 | 33.5 | LIL |
| Al III | 18.8 | 28.4 | LIL |
| C III | 24.4 | 47.9 | LIL |
| He II | 24.6 | 54.4 | HIL
 |
| Si IV | 33.5 | 45.1 | LIL |
| O III | 35.1 | 54.9 | LIL |
| N IV | 47.4 | 77.4 | HIL |
| C IV | 47.9 | 64.5 | HIL |
| O IV | 54.9 | 77.4 | HIL |
| N V | 77.4 | 97.9 | HIL |
Classified as a HIL because
He II 1640 is a recombination line
and thus the upperionization potential is important rather than the lower ionization potential. |