I understand atomic emission and absorption spectra well - photons of a specific energy can be emitted or absorbed by atoms, if that energy corresponds perfectly to the energy difference between two states of the electron of the atom - but I don't quite understand how the photons are absorbed and emitted during this transition. What process or mechanism underlies this phenomenon?
For Emission: Does it have something to do with the electron being accelerated during the transition, and the accelerating electron radiates a photon? If so, is this process random? What would cause the electron to suddenly drop energy level(s)? Where does the force/impetus for this acceleration come from?
For Absorption: Do the electric and magnetic fields of the photon apply a force to the electron when it interacts with the atom? If so, why do photons of only one energy apply this force, and all others have no effect on the atom?