This process handles the Compton scattering of gammas. It should be
used (instead of G4ComptonScattering) when low energy details, such
as atomic shell structure, are important.
Note: "low energy" electromagnetic processes such as this should
not be used together with "standard" electromagnetic processes such
as G4eIonisation, or else unpredictable results may occur. The one
exception to this rule is that the standard process
G4MultipleScattering may always be used.