[O III] doublet
dotâye-ye [O III]
Fr.: doublet [O III]
The two → forbidden lines with → transitions from the upper → energy level 1D2 of the doubly ionized oxygen atom. They occur in the green part of the → visible spectrum and are called → nebular lines. They are λ5006.8 1D2-3P2 and λ4958.9 1D2-3P1. Theoretical values for the [O III] 5007/4959 line-intensity ratio is 3.01 (Storey and Zeippen, 2000, MNRAS 312, 813).
[O III], spectroscopic notation of the ion O++; → doublet.