X-rays are made to impinge on
the surface of of a sample at glancing incidence
such that total reflection occurs. The X-rays
excite atoms in the top layers of the material
and the fluorescence is detected by a Si(Li) detector
) placed above
the sample. The technique is sensitive to very
dilute quantities of material (a few parts in
), but does require very flat samples.
The X-ray source can be an X-ray tube, or a synchrotron.