Apologies if I have done this wrong, it's my first post.
To my understanding, atoms can be excited by a collision of an electron or photon with sufficient energy to excite the electron into a higher energy level.
With an electron collision, it just needs enough kinetic energy to transfer into the atom for the electron to get into a higher energy level. With a photon collision, it needs exactly the amount of energy as the difference of energies between energy levels in the atom. If it has too little energy, the electron wouldn't be excited and hence the photon wouldn't interact, and the same with if it had too much.
My question is why cant the photon, similarly to the electron collision, collide with the atom with more energy than the difference in energy levels in order to excite the atom and then, to conserve momentum (similarly to how the electron continues with less momentum following a collision), why can't a new photon be emitted with a lower frequency?
Is this because momentarily the system would not conserve energy? If so, why cant a lower frequency photon be emitted instantly when the particles interact, similarly to how an excited electron instantly jumps to a higher energy level?