Elemental quantification using multiple-energy x-ray absorptiometry

A novel implementation of multiple-energy x-ray absorptiometry (MEXA) for e lemental quantification has been developed. Species are resolved on the bas is of their differential attenuation spectra across a wide energy range, id eally including absorption edges. By measuring the incident and exiting x-r ay spectra and using known values of mass attenuation coefficients over sel ected energy bands, the density line integral of the species along the x-ra y path can be calculated from all the selected energy channels simultaneous ly by non-linear least squares methods. Effects of 'escape' peak phenomena are modelled and corrections for them are included in the MEXA software. Th e applications of MEXA are illustrated by single measurements on aluminium and zirconium foils, quantitation of aqueous KI diffusing into a porous sol id, simultaneous measurement of acidic diffusant (CH2ICOOH) and porous soli d with which it reacts and which it dissolves and microtomographic reconstr uctions of liquid and solid specimens containing caesium and/or iodine.