As the atomic selection rules says that s to s transitions are not allowed i.e. there must be a change of the angular momentum ?
The dipole selection rules are only for optical transitions. you are correct, according to the dipole selection rule s to s transition is forbidden, that means light can’t make transitions. That’s why the atom is excited by collision which do not follow any rule.
Just been reading up on two photon emission (TPE) as a way to make the s to s transition whilst conserving angular momentum. Seems like it is not well understood or researched and is very rare.
A. Kani has it exactly right - the population inversion in HeNe is caused by atomic collisions, which populate an excited state of Ne which undergoes a radiative transition to another excited state of Ne. The light you see in HeNe is exactly at one of the wavelengths emitted by the "neon signs" which you have seen many times.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Atomic, Molecular and Optical Physics