Question on angular momentum changes of + or - 2

[Creator]

Guess I should know this but...

Maybe a good quantum guy can help me out.

In atomic transitions involving orbital angular momentum, L, (or total angular momentum J) , how is a change of + or - 2 accounted for??
Usually it is said that electromagnetic transitions are forbidden (presumably because they must change by + or - 1); therefore in a 0 to + 2 transition what happens to the excess (loss or gain) in angular momentum ?? How is it accounted for if not radiated electromagnetically?

Creator[?]

 

[RedX]

I'm interested in what happens too. Photons can only have +-1 definite angular momentum, so I think if the atom doesn't have +-1 momentum along the z-axis, then it can't emit a photon along that axis. So I guess for a total angular momentum quantum number of 2 and component of angular momentum along the z-axis of 2, you'd have to use the rotation matrices and find a direction where there's some amplitude to be in m=+-1, and the photon will be emitted in one of those directions.

 

[R0man]

It's understandable that you may not be familiar with the specifics of angular momentum changes in atomic transitions. In atomic physics, the angular momentum of a system is quantized, meaning it can only change in discrete increments. This is due to the fact that angular momentum is a conserved quantity and can only change through interactions with other particles or fields.

In the case of atomic transitions, the change in angular momentum is typically accounted for through the emission or absorption of photons. These photons carry away the excess or deficit of angular momentum, allowing the atomic system to transition between different energy states.

However, as you mentioned, there are cases where electromagnetic transitions are "forbidden," meaning they cannot occur through the emission or absorption of photons. In these cases, other mechanisms such as collisions with other particles or interactions with external fields may be responsible for the change in angular momentum.

Overall, the specific details of how a change of + or - 2 in angular momentum is accounted for in atomic transitions would depend on the specific system and interactions involved. But in general, the concept of conservation of angular momentum holds true and any changes must be balanced out through interactions with other particles or fields. I hope this helps clarify your question.