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Question Decays of Kr83m and the 9.4-keV state 

Forum: Hadronic Processes
Date: 28 Jan, 2011
From: Kareem Kazkaz <Kareem Kazkaz>

Hello all.

I would like to use the RDM to get decays of Kr83m. We start with Rb83, which gives us the Kr83m, which then decays properly within GEANT4 to Kr83. My question concerns the timing of the decays.

I set both the /grdm/verbose and /tracking/verbose to 4, and recorded the global times of the various decays. The Kr83[562.0] was created at 2.090776589788078e+16 ns. This in turn created Kr83[41.6] at the exact same time. This makes sense in this context because all the states between the 562.0 and 41.6 level have half lives on the order of 1-10 ps, but we are limited to 10-ns accuracy.

The Kr83[41.6] created a 32.1-keV electron at 2.090917703125662e+16 ns. This difference in decay time is reasonable, as it turns out to be 1411 seconds, and the Kr83[41.6] has a half-life of 9504 seconds.

Here's where it goes strange. A Kr83[9.4] is created at the same time as the 32.1-keV electron. This excited state should live for 147 ns according to the Table of Isotopes. Instead, the resulting 9.4-keV electron is created at the same time as the 32.1-keV electron. Within our simulation, we would like these two electrons to be correctly separated in time.

Buried in all the output were these lines:

...

*********************************************************************************************************
* G4Track Information:   Particle = Kr83[9.4],   Track ID = 56,   Parent ID = 9
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0 -3.21e-08 3.59e-08     -146         0        0        0         0 LiquidXenon initStep
G4RadioactiveDecay::GetMeanLifeTime() 
KineticEnergy:0[GeV]Mass:77.21571208485898[GeV]Life time: -1[ns]
mean life time: 0[s]
...

Note that the life time of this 9.4-keV state is -1 ns, which I assumes forces the the Kr83[9.4] to decay with no time delay. A couple dozen lines later I found

... G4DiscreteGammaDeexcitation::CanDoTransition - Excitation 0.009405100005096756, Min-Max are 0.0094053 6.3734 ...

Note that the energy of the 9.4-keV state is below the excitation minimum.

Two questions: Could this be what's causing the half life to revert to -1 ns? And how do I fix this to get the correct decay timing?

Thanks for any and all help!

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1 Feedback: Re: Decays of Kr83m and the 9.4-keV state   (Laurent Desorgher - 11 Feb, 2011)
(_ Warning: Re: Decays of Kr83m and the 9.4-keV state   (Laurent Desorgher - 11 Feb, 2011)
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