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Forum: Hadronic Processes
Re: Question G4DynamicParticle effective charge (sauvestre)
Date: 10 Aug, 2007
From: Vladimir IVANTCHENKO <>

On Fri, 10 Aug 2007, sauvestre wrote:

> *** Discussion title: Hadronic Processes
> Email replies to must include:
>   In-Reply-To: <"/hadronprocess/760">
>   Subject: ...change this to be about your reply.
> i am using geant4 v4.8.2.p01 and i am interested in the effective charge
> of recoil target nuclei impinged by incident neutrons. Thus i have used
> the G4DynamicParticle class to extract the effective charge of 12C via
> GetCharge(). As expected, the average effective charge increase if the
> incident energy is increased and for the energy range investigated 12C
> target nuclei recoil with an effective charge ranging from 1.47 ( 1 MeV
> incident neutron ) to 1.63 ( 19 MeV incident neutron ). Nevertheless, if
> i now want to see the electron occupancy in orbitals K,L (
> GetOccupancy(0),(1))as well as the total occupancy i find 0 in both case
> which means , if i am right, that the nucleus is fully stripped. How can
> i interprete such a result? thanks in advance.


Inside Geant4 the infrastructure fro this type of physics is ready, 
however, the implementation of this physics is limited. With 8.2 we have 
only effective change model, which means very strong assumption of 
equilibrium between ion and media. It is known, that in solid media the 
relaxation time is very short and ion travel in equilibrium condition, so 
we can reasonably simulate its energy loss and range. In this model 
effective ion change is not integer but some mena value depending on 
media and ion velosity.

Your task seems to be different - you express interest to recoil after
inelastic interaction, this physics is not well addressed inside Geant4.  
With 9.0 we decide make small modification: ion is produced fully ionized
in hadronic interaction. If the standard process G4ionIonisation is used,
than effective charge approach is applied. It is also possible to have
another process, which can have different model of ion/media charge
exchange. So, if in 8.2 only one model was possible, after 9.0 it is
possible to apply different models, which can be developed.

What we do not have for the moment is the simulation of slow recoil ion  
which keeps electrons after elastic or inelastic nuclear interaction.
This can be implemented but one needs to have corresponding model.


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