I know this, but I don't "see" it. What does "take place via dipole operator acting between the states" mean? I know this is the way one usually says and then there are selection rules and so as you say some transitions are forbidden.
Hi everyone, I'm a new member but it's not the first time I look at the forum.
Well, I don't know if this is the right section to post my question. I think it is related to quantum mechanics interpretation too. Anyway, let's have a look at my problem.
I've computed cross section for photon...