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Forum: Hadronic Processes
Re: Question nuclear excitation (Christian Stahl)
Date: 15 Oct, 2010
From: Michael H. Kelsey <Michael H. Kelsey>

On Sat, 16 Oct 2010 01:43:09 GMT, Christian Stahl wrote:
> hi there, I've written a process that shall excite a moving nucleus.
> Cross-section, kinematics, secondary emission etc are implemented. I
> tried to find out how to implement the excitation of the nucleus (giving
> the nucleus the property "is excited"), but got lost in the code
> browser.. Can sb please help me and tell what methods to use for the
> handling of excitation (and de-exctitation by gamma emission)? Ideally,
> I would like to provide the level scheme for the nucleus by myself.
> thanks a lot in advance, christian

What you're looking for is "pre-compound." If you already have a process written, then set it up to call G4PreCompoundModel::DeExcite(G4Fragment*). You will need to instantiate G4ExcitationHandler and register it with G4PreCompoundModel at construction. See the hadronic builders in source/physics_list/builders/ for examples.

You instantiate G4Fragment with A, Z, and a G4LorentzVector. If the latter has a mass larger than the ground-state mass of the nucleus, that is taken as the excitation energy. If you want to specify a "wounded nucleus" (i.e., with excitons, holes, etc.), there are G4Fragment::Set functions to do that, but you don't have to.

The level scheme is already handled for "all" nuclei (1746 isotopes, from He-5 to Cf-250) in $G4LEVELGAMMADATA. I don't know if there's a way to override that for a specific nucleus, without replacing the level-data file that is in the PhotonEvaporation2.0 package.

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