Theoretical model for the calculation of interference effects in TXRF and GEXRF

Interference effects between the contributions of transmitted and reflected radiation are observed during x-ray propagation at grazing angles in strat ified media. This phenomenon affects the fluorescence intensity in grazing incidence experiments [total reflection x-ray fluorescence (TXRF)] and graz ing emission experiments [grazing emission x-ray fluorescence (GEXRF)], thu s producing a characteristic interference pattern in the fluorescence spect ra. The theoretical description of this effect can be studied by using mode ls based on the general problem of an electromagnetic wave propagating thro ugh a stratified medium. In this work, a new approach to this problem is pr esented based on the development of approximations in the electric field. T his approach uses a new theoretical formalism introduced recently. By using this new model, we proved that in order to evaluate the interference effec ts of an electric field in any surface layer, the influence of the surface layers over the layer analyzed can be neglected. By using this result, the precision obtained in the calculations of an electric field is acceptable. As an example, we present theoretical calculations for x-ray propagation at glancing angles in testing stratified structures. The usual theoretical mo dels for data analysis of TXRF and GEXRF experiments can be simplified by a pplying the present model. Furthermore, our results allow a better understa nding of the experimental data obtained with both techniques. Copyright (C) 2001 John Wiley & Sons, Ltd.