Migration of chlorine in the X-ray fluorescence analysis of rocks

The intensity of the analytical ClKα-line continuously increases during the measurement of a rock sample. The main cause of this effect is the migration of chlorine into the irradiated (emitting) part of the sample. The hypothesis was credibly proved through the experiment in which a rock sample was measured first on one side, and then on the other. An increase in the intensity of the analytical line was observed in both measurements. The intensity in the second measurement registers an increase from the same or even the lower level than in the first part. The following chlorine migration model is proposed. Negative chlorine ions arise in the rock sample under the influence of primary X-ray radiation. X-ray photons knock out part of the ions from the sample; therefore, a positive electric field is formed in it at the sample–vacuum interface. It attracts chlorine ions from the depths of the sample, as well as chlorine ions flying outside. Thus, the number of chlorine atoms in the surface layer of the sample increases and consequently, the intensity of the analytical line of chlorine increases. Formation of chlorine ions, their migration, and concentration in the surface layer of the sample occur only under the influence of primary X-ray radiation.