Plasmon Excitations in Penelope


i simulate electron backscattering (18.6 keV, perpendicular to the surface) from a gold target and i have seen some strange peak structures right after the elastic backscattering peak (only with Penelope not with Livermore, Emstandard_Opt4, EmstandardSS). My first guess was that it corresponds to Energy Loss due to Auger Excitation but in a different work, with a different simulation tool these structures were assigned to plasmon excitations.

My Question is, are plasmon excitations part of the penelope model? I’ve found nothing about it in the official physics reference manual. However, in the Penelope 2018 Documentation plasmon excitations are at least mentioned.

Best wishes,

Dear Marco,

my impression is that the Penelope physics models, as implemented in Geant4, do not consider plasmon excitations. You may want to send an e-mail to Luciano Pandola, who included the Penelope models in Geant4. Luciano Pandola

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Dear @Marco78,

sorry, I had missed the question. The Geant4 Penelope models are based on the v2008 version of Penelope. I don’t know exactly the recent developments in v2018, but the Geant4 version also calculates the plasmon excitation energy and uses it to simulate ionization. The relevant calculations are performed in G4PenelopeOscillatorManager::BuildOscillatorTable()
One major difference with respect to Penelope is that there is no way in Geant4 to feed the information about the material being a conductor or an insulator. As default, the material is taken as an insulator, and “re-classified” as a conductor only if there is a very high plasma energy and oscillator strength. If you set a verbosity level of 2 to G4PenelopeOscillatorManager, you will see printouts like
Estimated oscillator strength and energy of plasmon:
XXX is a conductor/insulator

Hope this helps

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Dear Pandola,

thank you! This was very helpful!

Best wishes,