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I'm studying photoionisation and photodissociation, and I'm having a hard time trying know the microscopic details of such processes. I've read that in a photoionisation the photon is absorbed by a bounded electron in a atom (or molecule, or ion), causing the detachment of the electron if the photon's energy is higher than the binding energy. Also the remaining photon energy contributes to the kinetic energy of the now free electron. But does the photon really hit the electron, or it hits the whole atom, exciting it, until a detachment occurs?

This doubt emerged after thinking about photodissociation. In photodissociation there's a detachment of heavier particles (atoms, molecules and ions). Is the remaining photon energy also transferred to only one of the heavy particles that constitute the initial one? It seems not fair. Maybe it is transferred to both. And maybe in photoionisation the remaining photon energy is transferred to electron and ion, but by some reason the fraction received by electron is much bigger. Can you help me clarifying this problem? Also, can you suggest good references which explain more deeply these topics?

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You are correct in thinking that both the electron and ion share the photon's energy. Due to conservation of momentum and the fact that the ion Is much more massive than the electron, the ion receives only a tiny share of the energy.

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