Forbidden line

高温，低密，碰撞激发

nebular line

• forbidden line that is found in the spectra of → interstellar → ionized gas. The nebular lines are emitted by several atomic species (e.g. O, O+, O++, N+, S++) and correspond to the → transition from the electronic → metastable state 1D to the → ground state 3P. Examples are the doubly ionized oxygen lines [O III] at 4959 and 5007 Å.

auroral line

• 1) A prominent → forbidden line in the spectra of the aurora at wavelengths of 5577 and 6300 Å giving the aurora its characteristic green and red colors. Both are emitted by atomic oxygen, the former in its transition from the second lowest excited electronic state (1S) to the lowest excited electronic state (1D), the latter in its transition from the lowest excited electronic state (1D) to the atomic ground state (3P). (本意）

• 2) A forbidden line emitted by interstellar ionized gas by several atomic species (O, O+, O++, N+, S++, etc.) corresponding to the transition from the state 1S to 1D. (In astrophysics)

transauroral line

• A forbidden line emitted by interstellar ionized gas by several atomic species (O, O+, O++, N+, S++, etc.) corresponding to the transition from the electronic state 1S to 3P. Examples are the ultraviolet line of the doubly ionized oxygen [O III] at 2321 A and [N II] 3063 A. → auroral line; → forbidden line; → nebular line.