Energy levels of the C⁺ ion. P₁₄ = 100% indicates that a C⁺ ion in level 1 can be photo-excited only to level 4. The green numbers are the probabilities that a C⁺ ion in level 4 radiatively de-excites to level 1 or 2. The red numbers are the probabilities that an incoming photon with a wavelength between 1335.66 Å and 1335.71 Å hitting a C⁺ ion in level 2 excites it to level 3 or 4. P₃₂ = 100% indicates that a C⁺ ion in level 3 can only radiatively de-excite to level 2.