X-ray fluorescence (XRF) occurs when the inner shell electrons of atoms in a sample are excited by incident X-ray photons (synchrotron beam). As the system relaxes, electrons transition from higher energy levels to the vacant inner shell, releasing an X-ray photon in the process.
About XRF
Technique
The photoelectric effect
The beauty of this process lies in the fact that each secondary X-ray photon (often called characteristic radiation) emitted from the sample has a specific energy unique to the atom from which it originated. By measuring the energy of these secondary photons, it is possible to determine the elemental composition of the sample at the point where the X-ray beam interacts with it.
In µXRF mapping, a focused spot is used to illuminate a small section of the sample, allowing for the determination of composition at that specific point. By moving the sample in a grid pattern, we can build up a 2D image of the varying composition pixel by pixel.
Using calibrated standards, synchrotron XRF can be made into a quantitative technique.