Hi all. I have been thinking about this problem for quite a while now. Still kinda clueless. We know that when we apply electromagnetic radiation on an atom/molecule, then depending on the frequency of the radiation the atom/molecule makes electronic transition. We know how to get the average energy absorbed per unit time by the atom. But what is the average force acting on the electrons during that process. I know the average force can be obtained using Ehrenfest theorem. But how do I apply it for the transition process. Any help greatly appreciated.