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None Does GEANT4 model E1, E2, M1, M2 gamma emission profiles? 

Forum: Hadronic Processes
Date: 06 Jul, 2011
From: Anuj Kapadia <Anuj Kapadia>

Hello all,

I'm developing a simulation to model the angular distribution of gammas around an iron target bombarded with 5 MeV neutrons. For a 56-Fe target, inelastic scattering gammas are expected to be emitted at mainly 847 keV, corresponding to the transition from the first excited state to ground state. This transition is known to exhibit an electric quadrupole (E2) emission profile. Does Geant4 account for the angular distribution of the gammas around the target? If so, then where is this information located?

Looking through the source code, the de-excitation of the nucleus appears to call the "G4NeutronHPDeExGammas" class, which lists the following code for theta-phi sampling: (see attached image; also available at http://lcsim.org/software/geant4/doxygen/html/classG4NeutronHPDeExGammas.html)

Lines 77 to 82 of this code suggest that theta is modeled as a cosine function, whereas phi is a uniform distribution from 0-2pi. Is this true for all energy level transitions and isotopes, or are dipole, quadrupole, octopole profiles modeled specifically?

Thanks.
Anuj

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