Principle of XRF and PIXE techniques

The principle of both of these techniques is to excite the atoms of the substance to be analyzed by bombarding the sample with sufficiently energetic X-rays/y-rays or charged particles. The ionization (photoionization for XRF and ionization caused due to Coulomb-interaction in case of PIXE) of inner-shell electrons is produced by the photons and charged particles, respectively. When this interaction removes an electron from a specimen s atom, frequently an electron from an outer shell (or orbital) occupies the vacancy. The distribution of electrons in the ionized atom is then out of equilibrium and within an extremely short time s) returns to the normal state, by transitions 

The designation of various K and L X-ray transitions to denote transitions of electrons is given in Table 1.1. 

As mentioned earlier, the spectroscopic notation for X-rays will be as  

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