CALCULATION OF INTENSITIES IN GRAZING-EMISSION X-RAY-FLUORESCENCE

The sensitivity of x-ray fluorescence spectroscopy to surface and subs urface layers in the nanometer regime can be greatly enhanced by measu ring the fluorescence radiation that is emitted at grazing angles. In this paper, we present a formalism for the calculation of x-ray fluore scence intensities that is also valid under grazing emission condition s. By applying asymptotics to plane-wave expansions, an approximate so lution to Maxwell's equations for a radiating point source in a layere d system is derived, without the use of the optical reciprocity theore m. In the computation of the fluorescence intensity, secondary and hig her-order fluorescence effects are taken into account. The total fluor escence of a particular layer is obtained by integrating the contribut ions of point sources at different depths. The derived expressions com pare well with the measured angular dependence of the fluorescence int ensity in a number of typical examples.