When incident light passes through a hydrogen gas, for example, does it have 50% chance (since it's a 1:1 ratio of protons to electrons) of getting absorbed by the proton? Any chance at all? If no, why not? Does a proton have a "bandgap"? If yes, what happens when a photon is absorbed by a proton?
Atomic Physics – Can a Proton Absorb a Photon?
absorptionatomic-physicsphotonsprobabilityprotons
Best Answer
A system can absorb a photon if the energy of the photon matches an excitation in the system. So the hydrogen atom can absorb a photon if its energy matches one of the frequencies in the hydrogen spectral series.
A proton is a composite object and it does have a spectral series. However the excited states of the proton involve rearrangements of the energy and angular momentum of the partons that make it up. The transition energies are in the 100MeV to 1GeV range so they are far beyond anything that could be excited by visible light. However gamma ray photons could excite such transitions and be absorbed.