Some considerations on thick sample thickness in X-ray fluorescence analysis

In this work, the problem of the assessment of thickness for a thick sample in the case of polychromatic excitation has been considered. For a given sample composition, such a thickness (more precisely a product of the sample thickness and density) can be calculated easily in the case of monochromatic excitation—for which an analytical solution of the Sherman [J. Sherman, Spectrochimica Acta, 1955, 7, 283–306]/Shiraiwa–Fujino [T. Shiraiwa and N. Fujino, Japanese Journal of Applied Physics, 1966, 5, 886] equations can be found. For the polychromatic case, however, such a solution does not exist. In this work, some approximations of the problem are discussed and compared with a full solution acquired in an iterative way.