G3 to G4
Photo electric effect

Total cross section, Mean free path, Binbing energies

• Geant3
  S(E,Z): Sandia parameterisation.
  

• Geant4 standard
  Egamma > 50 keV: copied from Geant3.15:
  
  • B(Z): parameterisation of K, L1, L2 shells (4 parameters per shell)
  • S(E,Z): parameterisation from L. Urban (total: 20 parameters).
  Egamma < 50 keV:
  • B(Z): table for all shells, all elements.
  • S(E,Z): from Sandia parameterisation (updated coefficients).

• Geant4 low energy
  B(Z) and S(E,Z) extracted from EPDL97 data set.
  from 250 eV to 100 GeV.
  

Final state

• Geant3
  Tkin e- = Egamma - B(Z) (an effective Z is used in composite).
  e- emitted in direction of incident gamma.
  

• Geant4 standard
  Choose randomly an element within material.
  B(Z) read from full table.
  emitted e- as in Geant3.15
  

• Geant4 low energy
  Subshell cross sections from EPDL97 are used to select randomly the first subshell ionised.
  Photo electron emitted as in Geant4 standard.
  Fluorescence photon cascade emitted isotropicaly; (transition probabilities extracted from EADL data set).