Specifically, I am wondering about the angular momentum selection rules. For a 1-photon ionization, since the photon has 1 quantum of angular momentum, I think the change in the total orbital angular momentum of the molecule would have to be +/- 1. And for a 2-photon ionization, which I'm trying...
Question: For ionization of a homonuclear diatomic, how do the selection rules differ for a nonresonant 2-photon ionization process and a 1-photon ionization process?