What's happen when a molecule or an atom is already in an excited electronic state and is hit from another photon? Example 1: my molecule absorbs a VIS photon (there's a time in which the molecule is an upper electronic state before the re-emission or etc. etc. process) what happen if another photon with the same wavelenght hit it in the while? Example 2: and if a photon of another wavelenght (e.g. IR)?