Practical Aspects of Absorption Edge Spectrometry

Abstract

Since each element has ionisation edges at characteristic energies, the main aspect in edge spectroscopy is elemental analysis. The task of deciding which element(s) a particular sample consists of, is relatively easy to perform by observation of structure at ionisation energy losses in the elsewhere smooth spectrum. Quantitation of loss spectra is quite another story, complicated by such facts as insufficient knowledge of cross sections, instrumental aberrations and instabilities, or masking effects (background intensity, multiple scattering, etc.). At present an accuracy of 20 % in quantitation seems to be realistic, although better figures have been obtained in particular cases [3.1], [2.19]. The same holds for the lower detection limit of mass fraction which is, for routine application, on the order of 5 atom % [3.18], whereas under special circumstances, minima of some 0.01 at % [3.10] to 0.5 at % [3.2] are given. As to the absolute lower detection limit, there are several calculations, yielding some ten atoms [3.19], [3.9] up to some 100 atoms [3.20].