The Wikipedia article on photoelectric effect has the following line:

Electrons can absorb energy from photons when irradiated, but they usually follow an "all or nothing" principle. All of the energy from one photon must be absorbed and used to liberate one electron from atomic binding, or else the energy is re-emitted. If the photon energy is absorbed, some of the energy liberates the electron from the atom, and the rest contributes to the electron's kinetic energy as a free particle.

Now, the Wikipedia entry uses the word "usually" rather than "always", so are there any cases where this "all or nothing" principle is not followed?

PS: exclude the case in which an orbit transfer may occur.

  • $\begingroup$ Raman scattering is one. $\endgroup$ – Jon Custer Oct 25 '17 at 14:22

Compton scattering can be considered as a clear counter-example: a photon of reduced energy is in the final state, along with an electron of increased kinetic energy.

  • $\begingroup$ In the terminology of gamma-rayspectroscopy, Compton scattering and photoelectric effects are clearly differentiated, as can be seen e.g. in en.wikipedia.org/wiki/Gamma_spectroscopy#Detector . So in this language, the Compton process is not a subset of the photoelectric effect. $\endgroup$ – Ezze Oct 7 at 12:20

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