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I'm undertaking a bit of work looking at a Background Gamma Spectrum. On the spectrum, I have a clear, tall line at 834 KeV. I have a PDF file of a table of Gamma Spectra (ordered in energy) from Natural Radionuclides. If I look for 834 KeV in the list, it gives me Germanium 72, at this energy level. If I now look across at the "Intensity" column, unlike the vast majority of other Nuclides, the table simply gives a double dash. The decay mode is given as Neutron - Neutron & Gamma. My question essentially is why is no intensity given? Is there a specific reason which I'm missing? It's a similar case for other places in the table with Neutron Capture involved.

Many thanks, hope this is clear enough.

Matt

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    $\begingroup$ Are you sure that it is Germanium-72? Actually, it is a stable isotope and it should not have any decay mode. Can you please tell us which table you are using to search for radionuclides? There is also Mn-54 which emits 834 keV gamma radiation, but it is relatively unstable so I doubt that it's easy to find its presence in background radiation. $\endgroup$
    – Chaosit
    Commented Aug 12, 2015 at 12:46
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    $\begingroup$ As for no intensity for neutron capture - that is not a natural decay (which happens without external influence) like alpha or beta decays - this is an interaction of the nucleus and a particle and it is characterised by cross-section, thus the intensity will depend on the intensity of the neutron beam, amount of Germanium, energy of neutrons (since cross-section is dependent on it), geometry of the experiment and who knows what else $\endgroup$
    – Chaosit
    Commented Aug 12, 2015 at 12:49
  • $\begingroup$ @Chaosit Those two comments combined look like an answer to me. $\endgroup$
    – ragnar
    Commented Aug 23, 2015 at 23:03
  • $\begingroup$ @ragnar, well I just wanted to clarify some things before actually posting the answer (and first comment was a result of paying not enough attention to the question), but, apparently, OP has already fond answer somewhere else. $\endgroup$
    – Chaosit
    Commented Aug 24, 2015 at 8:09

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Just wanted to summarize my comments:

Are you sure that it is Germanium-72? Actually, it is a stable isotope and it should not have any decay mode. Can you please tell us which table you are using to search for radionuclides? There is also Mn-54 which emits 834 keV gamma radiation, but it is relatively unstable so I doubt that it's easy to find its presence in background radiation.

As for no intensity for neutron capture - that is not a natural decay (which happens without external influence) like alpha or beta decays - this is an interaction of the nucleus and a particle and it is characterized by cross-section, thus the intensity will depend on the intensity of the neutron beam, amount of Germanium, energy of neutrons (since cross-section is dependent on it), geometry of the experiment and who knows what else

Actually if you post your spectrum it will be much easier to understand what is going on there

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  • $\begingroup$ Your answer was very informative, and whilst my question wasn't answered, I've realized since two weeks ago that it's not really a question that has answers at all. The table I was using was a '98 PDF of Background Gamma Energies and their related info (cross sections, decay mode etc). $\endgroup$
    – Matt
    Commented Aug 24, 2015 at 9:20

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