Congrat's on that astute finding Dave!
?May I suggest that much of that is probably NOT self-XRF in the sense we are talking about, rather it is the normal characteristic X-Rays given off by the daughters within the decay chain at the moment of transmutation.
For an easier to understand example, when Cs-137 decays to Ba-137m (m=metastable, meaning stable but for a very short time, in this case 2.5 min) by beta decay, it is the daughter realigning it's nucleus excess energy that gives rise to the "662" plus in this action the electron shells are irradiated causing XRF OF THE DAUGHTER ATOM's characteristic energies.
If it was truly self-XRF, the X-Rays would be of energies characteristic to Cs atoms.
In a simple radioactive decay to a stable or metastable element, this relationship is clearly measurable, but in a decay chain of any length, things are so complex it's really? hard to make heads or tails of the jumble of closely spaced X-Rays.
When in doubt consult the RL Heath Gamma Spectrum Catalogs both for NaI(TL) and Ge-Sil.
Links to those:
?and if you don;t have the freeware program DECAY, it should be here (I like the March 1999 version3 best):
With this program you can look up many of the decay chain daughters individually and learn where those alphas, betas, other electrons and gammas actually come in.
Geo
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On 2018/10/21 06:11 PM, David Eckhardt wrote:
Self Excitation:? In working with Luuk's new (to me) 2" x 2" CsI 'puck', I was quite surprised to detect self excitation of
the Bi, U, and Ra XRF lines using a small chunk (1 x 0.5 x 0.2 cm) of uraninite as the source.? After doing a three-point calibration
using both Cs-137 and Am-241 of the low end, the lines were right on.? Of course, I had to 'fine tune' Theremino to bring
out the XRF lines, but they were clearly there. ? I haven't yet tried copper with this new probe, but that will be excited with an
Am-241 pellet.?
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Dave - W?LEVOf course, I had to d? ?
Very interesting Charles. Normally I discount self-XRF ideas but your scans make a compelling argument. Will look into that in future...
Meanwhile you can get some elemental cerium (glass polish etc) and irradiate it with a weak source, to make a pure, clean set of Ce K lines for you calibration setup. This is one of the really helpful aspects of XRF, make your own absolutely precise spectrum lines!
Geo
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Dave - W?LEV
Just Let Darwin Work
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