G3 to G4
Rayleigh scattering

Total cross section, Mean free path, Form factor

• Geant3 (optional)
  S(E,Z): parameterisation from G. Tromba (4 parameters per element).
  Fit from ? to ?.
  

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

Final state

• Geant3 (optional)
  Atomic form factor F(E,Z): parameterisation (~8 parameters per element)
  Sample the gamma angle from Rayleigh differential cross section, which depend of the form factor.
  

• Geant4 low energy
  select randomly an element within the material.
  Atomic form factor F(E,Z) extracted from EPDL97 data set.
  Angular distribution is Rayleigh distribution multiplied by form-factor square.