About Si characteristic X-ray energy

Physics Processes, Models and Cross Sections
1

Dear Geant4 experts,

Hello,
I’m Hyeonseok Do, and I’m developing a Si detector simulation using Geant4.

I’ve just checked the characteristic X-ray energy of Si using Geant4.
Theoretically, I found the Ka of silicon is 1.74keV.
But when I checked it using Geant4, the value was 1.72keV.

스크린샷 2026-03-23 12.18.15
스크린샷 2026-03-23 12.18.151020×580 9.72 KB

It’s just a little difference, but do you know the reason?
I just collected all secondary particles and got the energy directly.

{
      const auto* secondaries = step->GetSecondaryInCurrentStep();

      for (const auto* sec : *secondaries) {
        if (!sec) continue;
        if (sec->GetDefinition() != G4Gamma::GammaDefinition()) continue;

        const G4double EkeV = sec->GetKineticEnergy() / keV;
        fRunAction->RecordSiSecondaryGammaEnergy(EkeV);

        const G4VProcess* creator = sec->GetCreatorProcess();
        const G4String creatorName = creator ? creator->GetProcessName() : "";

        // bremsstrahlung gamma
        if (creatorName == "eBrem") {
          fRunAction->RecordSiSecondaryGammaBremEnergy(EkeV);
        }

        // Si characteristic X-ray candidate
        if (procName == "phot" && EkeV > 0.0 && EkeV < 2.0) {
          fRunAction->RecordSiSecondaryGammaCharCandEnergy(EkeV);
        }
      }
    }

But I cannot see anything in the 1.74keV bin.

Thank you for your help in advance.
Have a nice day.

Best regards,
Hyeonseok.