Every atom has electron shells surrounding the nucleus. In its most stable form, an atom will have the same number of electrons in those shells as it has protons in its nucleus.
Every single electron in the orbitals of the same elemental atoms (atoms with same protons #s) will be bound to the nucleus with individual unique binding energy according to that element's scheme .From one atom to the next, as long as they have the same elemental name and therefore the same number of protons in the nucleus, this scheme will be identical.
All identical elements will have the identical scheme. No two electrons in a given element will have the same binding energy, and no single electron in any different element's atoms can have the same binding energy as the first element. To recap, every electron in every element has a unique binding energy associated with that element only.
Upon application of extra kinetic energy to the atom, the electrons can pick up (absorb) some or all of that energy and some interesting things start to happen. This energy can be from various external sources and can be conveyed into the atom by X-Rays, Gamma Rays, and even charged particles such as energetic electrons or alpha particles.
Once an inner electron achieves a higher kinetic energy than allowed by its unique orbital, it will leave that orbital position and take up a higher orbital or even leave the atom entirely, leaving a hole where it was originally. Atoms MUST fill the innermost holes and do so with high priority. When an electron from a higher orbital fills that hole, the amount of energy equal to the binding energy ifs given off as an electromagnetic photon, which we call Characteristic X-Rays.
By measuring those X-Rays very closely we can determine the elements involved and even the orbital from which that hole was filled. By stealing another orbital's electron, there now remains a hole in that orbital which must be filled, and so on.
Orbitals in XRF work are labeled according to letters, starting with K for the innermost. Other branches fs science label those same orbitals with numbers, starting with 1.
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As mentioned, this "Fluorescence" of "X-Rays" (XRF) can be causedd by a number of energy sources and carriers. I have discovered that the combination of Gamma Rays and Alpha Particles from @59.5 make a very efficient excitation source. Sometimes only one pellet is needed (<1 uCi) and never have
more than 8 spaced around the target been needed.
Pictured below is a jig I designed with 8ea. 1/8th" holes into which are inserted the correct # of pellets for a task.Originally designed for the RAP-47 probe, this was called the RAP-CAP. It fits may other probes as you can see.
