Validty of Atomic Deexcitation at Energies < 150 eV

We are simulating compton scattering process in silicon by a 59 keV gamma source.
There seems to be a mismatch between the geant4 simulations and the measured data at the silicon L-step transition (100 eV to 150 eV).
Are the atomic de-excitation cross section libraries are up to date in the energy range less than 150 eV?

HI, did you activate the Auger cascade? It is shown in extented electromagnetic example TestEm5

Yes, I have activated the Auger cascade process.

Did you include the following UI commands in your macro?
/process/em/augerCascade true
/process/em/deexcitationIgnoreCut true

The command /process/em/deexcitationIgnoreCut true was not mentioned in my macro
So by default the deexcitationIgnoreCut flag was set to false. I am setting it to true and looking at the results now. In the mean time, could you tell me what the significance of ignoring the cuts is?


This command disables the use of production threshold for fluorescence x-rays and Auger electron production. This means that fluorescence X-rays and Auger electrons can be originated with kinetic energy lower than the corresponding energy of the range cut set in the simulation. This command is essential to describe correctly the atomic de-excitation.

Just a question: if we have set deexcitationIgnoreCut false, the fluorescence and Auger energy just gets added into GetTotalEnergyDeposit(), doesn’t it? Or is the energy from those atomic transitions simply lost?

Hi, the energy should be added into the GetTotalEnergyDeposit(). This is my understanding


Ciao Mike. Yes, I confirm what @guatelli said. All EM models enforce energy conservation, so - if secondaries are not generated - their energy is computed into the local energy deposit.

Here a macro to illustrate what Luciano said.
A gamma, 80 keV, triggers a photoelectric interaction in a block of Tellurium.
In the first plot, atomic deexcitation is not activated. Photo electron is generated alone (48.2 keV) and binding energy of the shell is accounted as local energy deposit. Hence total energy deposited is strictly 80 keV.
In the second plot, we can see gamma of deexcitation and Auger cascade (see also the detailed printout of 2 events). The total energy deposited is still 80 keV.

atomicDeexc.mac.txt (847 Bytes)