Self‐element secondary fluorescence enhancement in XRF analysis

In XRF analysis, the need for improved quantification approaches for non-homogeneous samples requires a better understanding of all the energy-dispersive spectrum features, in particular, the K/L or L/M intensity ratios among the characteristic x-rays of the same element. These ratios are affected by the secondary fluorescence contribution of the more energetic characteristic x-rays (K- or L-lines) to the corresponding one of lower energy (L- or M-lines, respectively). Theoretical calculations of the secondary fluorescence contribution among the characteristic x-ray lines of the same element (self-element secondary fluorescence enhancement) are presented for pure element targets by means of the fundamental parameter approach. For representative cases, the calculations were also performed for different exciting monochromatic x-ray beam energies and as a function of the target thickness. The calculations predict that for pure targets and monochromatic exciting radiation, the self-element secondary fluorescence enhancement contributes to the primary fluorescence intensity in a non-negligible amount, up to about 20-25%. An experimental approach is proposed for the estimation in thick pure targets of the relative increase of the M α,β fluorescence intensity due to the L-line self-element secondary fluorescence enhancement.