On optical energy loss function, it is said that we don't see the surface plasmon. However, we can see the plasmon peaks on reflection electron energy loss spectroscopy.

My question is that why electrons can excite the surface plasmon on flat surface but photons cannot (at least we dont see it on ELF). The photon/electron incidence is orthogonal to the surface.

  • $\begingroup$ This is basically a repeat of your question yesterday. $\endgroup$
    – Jon Custer
    Jun 26, 2020 at 18:04
  • $\begingroup$ @JonCuster And I am still seeking an answer. Is the question clear enough or not? $\endgroup$ Jun 26, 2020 at 22:38

1 Answer 1


It is due to a mismatch between photon and electron/plasmon momentum. The conservation of energy and momentum can not be met simultaneously if the incoming particle is a photon.

  • $\begingroup$ Can you describe it further? $\endgroup$ Jun 26, 2020 at 22:37

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