Fluorescence and optical photons

My question is hopefully a simple yes/no, does turning on the following via user commands while having the optical physics constructor included mean I can produce optical photons via fluorescence (x-rays incident on high density gases for example) or will it just produce gamma particles via fluorescence (cuts permitting of course)?

/process/em/fluo true
/process/em/auger true
/process/em/pixe true

The optical photons physics handle the transport of optical photons produced by scintillation and Cherenkov effect. The particle is an “optical photon”.

My understanding is that the optical photons you would like to produce come instead from fluorescence and they are “gamma” in Geant4. I am not sure you can produce such low energy photons (below 3 eV) with the atomic de-excitation package of Geant-4. Honestly I do not know. Try to run the simulation with /process/em/deexcitationIgnoreCut true. But still, let’s suppose you create them, they will not be transported because they are “gamma” and not “optical photons”.

Let me know how it goes,


1 Like

Is there a way to add deexcitation data for N2 easily down to optical range?

I am not sure. We have to check this. The easiest way is to ask to the Coordinator of the EM Physics. Eventually this could become a new User Requirement for Geant4 .


atom de-excitation process produce G4Gamma. Minimum transition energy in Geant4 DB is about few eV. Smaller energies cannot be produced in atomic de-excitation.