Quote:
Originally Posted by MortonH
Wonderful image.
What's a forbidden emission?  |
When an electron is raised to a higher energy level it emits a photon when it drops back towards the nucleus of the atom.
On Earth Nitrogen only exists as a molecule of N2. In the vast reaches of outer space the single Nitrogen atoms never or very rarely collide with another single Nitrogen atom to form a molecule of N2 or do not have enough electrons to have a party. So this lonely Nitrogen atom only interacts with the odd electron to emit so called 'forbidden' frequencies of light.
It is purely an historical term. The square brackets around the emission line [II] designate that the emission is forbidden. The prefix is the atom that is emitting ie N[II].
Bert