Question about a specific line on a gamma spectrum, here. Below is a background gamma spectrum observed by a Ge[li] detector.


I've been able to identify all the lines with mostly certainty, apart from one, highlighted, at 477 keV. I'm not sure whether I can attribute it to Be-7 as I don't understand why that would be present in the environment. I also can't see any process by which it could be being created. However, I can't find any other candidate isotopes. No other isotopes have emissions at energies which fit this spectrum.

Does anyone know of some process that might be producing Be-7? Does anyone have any other ideas?

  • 1
    $\begingroup$ Did you have a look at nucleardata.nuclear.lu.se/database/nudat ? There, you get a large tables of isotopes emitting 477keV: nucleardata.nuclear.lu.se/Scripts/database/nudat/… . However, you have to check which isotopes are reasonable, most seem to be a bit exotic. (Also, I wonder why Be7 is not listed...) $\endgroup$
    – sweber
    Aug 27, 2015 at 8:57
  • $\begingroup$ Very close, I use this one: nucleardata.nuclear.lu.se/toi/… As it was more regularly updated. You can find Be-7 there. $\endgroup$
    – Matt
    Aug 27, 2015 at 9:20
  • $\begingroup$ Beyrillium-7 is pretty exotic and can be made in cosmogenic processes, but the rate is tiny (events per square-cm per year...). It worth taking the lines you are confident that you have identified and checking the energy calibration of the device. My experience suggests that a fairly modest miscalibration in energy can lead to unnecessary struggles in identifying lines. $\endgroup$ Aug 27, 2015 at 14:32

1 Answer 1


Be-7 is common atmospheric radionuclide produced by cosmic ray spallation of nitrogen and oxygen. Ground level concentration of Be-7 is in order of ~mBq per cubic meter of air. Main deposition process of Be-7 is a wet scavenging which yields to ~Bq per litre of rainwater. It is therefore possible to find Be-7 in background (depends on location of measurement, obviously).

You could also check the spectrum for 1275 keV line coming from Na-22, which has the same cosmogenic origin as Be-7.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.