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PART-1 Definitions. Some are specific to the XRF sub-discipline.

Practicing XRF is what we do and discuss on this chat board.?
For those who are reading but aren't practicing XRF techniques yet, lets lay out some of the theory behind XRF-

First the initials stand for X-Ray Fluorescence.?
A few definitions of the noun fluorescence in layman is "shine" another is "glow"..?
For our our purposes the definition of General Science is a little more detailed:

1.??? The giving off of light by a substance when it is exposed to electromagnetic radiation, such as visible light or x-rays. As long as electromagnetic radiation continues to bombard the substance, electrons in the fluorescent material become excited but return very quickly to lower energy, giving off light, always of the same frequency. Fluorescent dyes are often used in microscopic imaging, where different dyes can penetrate and illuminate different parts of the sample being examined, helping to distinguish its structures.

Compare?

2.??? The light produced in this way

So in very basic terms, the "F" in XRF is to shine by means of energy transfer at an atomic level, and the XR part defines? the "light" we detect as being X-Rays. To make the atom fluoresce X-Rays can be done by a number of means, not always having to do with applying X-Rays to the sample. The external energy can come from an electromagnetic source of from charged particles like Alpha Particles and fast electrons. A lot of the XRF we look at are excited by the energy ejected from the nucleus of a newly created element a result of radioactive decay of its parent element. This latter X-Ray and Gamma Ray from the daughter is usually immediate, but can be delayed, sometime much longer. Such daughter elements are appended with the small letter "m" for metastable.
Check out Cs-137/Ba-137m decay scheme. Ba-137m has a half-life (T/2) of 2.55 minutes.

Remember radio waves, microwaves, infrared, visible light, ultraviolet light, X-Rays and Gamm Rays are all "light"- simply electromagnetic radiation of different energy levels..

In this practice we consider X-Rays as being electromagnetic energy being formed from the electron shell of an individual atom, while Gamma Rays originate within an atom's nucleus. Things will be a simpler in the long run if we all consider "Radioactive Decay" the? process that changes parent element to a different element# by changing the proton# in an atoms nucleus. Beta and Alpha decay are the most common, but there are many others.
Once the element has changed to it's new nucleus, there are secondary emissions from that element's nucleus- these include the Gamma Rays and the production of XRF from the daughter product's electron shells.

A very obvious example is the major radioactive check disc we use for calibrating XRF systems: Fe-55. It decays by Electron-Capture (EC) to Mn-55. If we apply an external energy to stable Fe, we get back the XRF energy of Iron Ka1= 6.40 keV (there are others too). If we turn off the external exciter and test radioactive Fe-55, on our instruments, we see X-Rays of the daughter which is 5.90keV. There's no mistaking the two with a Si-PIN or other high resolution detector.

Highlight- natural X-Rays from radioactive element are of the daughter, induced X-Rays of stable elements is of that element.

Important! Keep the above in mind as we discuss XRF.



Let's stop here for discussion, we can add more definitions later via the edit function.

Geo