Al28 labeled as Mg28

[lgordon]

I'm not exactly sure if this an issue but seems to be labeled wrong:

[wcjohns]

Hi @lgordon, I'm probably missing something obvious, but what part of this is mis-labeled? thanks, -will

[lgordon]

I think the parent column match the first element in the decay column, ie. Al28 in this case instead of Mg28? Also this energy 1778.85 doesn't correspond to 28Mg decay.

You can also see the Al28 decay energy listed incorrectly when you search Mg28

[wcjohns]

This is intended behavior, although perhaps a bit confusing at first, especially if coming from software that doesn't dynamically decay nuclides.

When listing gammas or x-rays of a nuclide in InterSpec, the gammas of the full decay chain are listed - at the specified age, since this is what we actually observe in measurements. So in your screen shot above, the age is 2.5 times the half-life (i.e. "2.5 HL") of Mg28. You could instead change this to zero seconds (i.e., "0 s" ); you would then see the gammas of just the Mg28 decay. And in your screen shot of the "Reference Photopeaks" tab, the "Parent" column indicates at which point in the decay chain the gamma is from, and in this case indicates Al28 (which Mg28 decays into) for the 1778.85 keV (and now that you point it out, perhaps naming the columns on both these tabs the same isn't the clearest - I'll think of better terms - thanks!)

And for the "Nuclide Search" tab, the matching is not on a single nuclide, but rather the entire decay chain of nuclides. For example, the 661.66 keV of Cs137 isn't actually from the Cs137 decay into Ba137/Ba137m, but if you see a peak at 661 keV, you are probably measuring a Cs137 source, and not a Ba137m source with half-life ~2.5 minutes, so it makes more sense for results to list Cs137, before Ba137m.

When the results are sorted by the "Profile" column, which is default, a few other factors also play in:

• The search results also take into account the other peaks present in the spectrum (even if you haven't fit them - an automatic peak search is performed in the background). So even though you are sorting on 1778 keV (potentially from Al28), if there is a peak in the spectrum at say 400.69 keV, which is from Mg28, then the source is likely Mg28, which decays to Al28, since Al28 alone wouldn't explain the 400.69 keV peak. Al28, as a parent nuclide will probably be listed further down the results - as long as T1/2 isn't set too high though.
• Al28 has a half-life of two minutes, where Mg28 has a half-life of 21 hours, so if you are seeing the source in a spectrum, Mg28 is more-likely than Al28, so will be listed first (although if gammas directly from Mg28 decay aren't seen, but would be expected, then Al28 still may be listed first).
• There are a few other heuristics associated with the ordering in the "Profile" column that help to match sources to what people generally expect

Hopefully this all makes sense. Please let me know if not.

[lgordon]

Thanks very much, I figured it was more likely I was misunderstanding. The spectra is from Al28 and shouldn't contain Mg28 but now I understand and it works as intended when you input the 0s.

[wcjohns]

A little bit of a re-vamp of the nuclide ID tab is planned, and I need to give it a little more thought, but I think it would be reasonable to have some sort of a "direct" or non-aged option, to help with situations similar to yours, or maybe kinda hint at meanings better - so thank you for creating the issue!