- #1
kof9595995
- 679
- 2
I guess this is a FAQ, but since it constantly confused me, I'm just going to ask anyway.
Two ways of exciting atoms, shoot a beam of photons and let atoms absorb them, or shoot a beam of electrons, and let atoms collide with them.
However, for the excitations to happen, the former case requires the photon energy matches the energy level differences exactly, and the latter case only requires kinetic energy of electrons bigger then energy difference. How should we explain this from first principles of QM or QFT?
Two ways of exciting atoms, shoot a beam of photons and let atoms absorb them, or shoot a beam of electrons, and let atoms collide with them.
However, for the excitations to happen, the former case requires the photon energy matches the energy level differences exactly, and the latter case only requires kinetic energy of electrons bigger then energy difference. How should we explain this from first principles of QM or QFT?