X-Ray Fluorescence - Multiple Transitions

Since most atoms comprise a number of electron orbitals (eg, K shell, L shell, M shell) a number of possible fluorescent transitions are possible.

For example, interaction of X-Rays with an atom with K, L and M shells could result in a hole forming in the K shell, which is then filled by an electron from the L shell or from the M shell. In either case, these are termed K transitions. Alternatively, a hole could be formed in the L shell, subsequently filled by an electron from the M shell (termed an L transition).

Thus, for a single element, a number of XRF peaks are possible, and typically these will all be present in the spectrum, with varying intensities. They form a characteristic fingerprint for a specific element.

XRF Peaks