Formalism for Thick-Target XRF

If the target is appreciably thick, a fraction of the incident photons gets absorbed by the target as they penetrate deep in the target material. Similarly a fraction of fluorescent X-rays emitted by the target are absorbed as they reach the surface of the target. Correction has thus to be applied to take care of these absorption effects. 

Let t be the actual thickness of the target (gcm ). To make correction t is replaced by tgff an effective thickness given by  

Here py and ix (in cm g ) are the mass absorption coefficients of the target material for incident photons and characteristic X-rays produced in the target with the impact of incident photons. Thus (1.22) gets modified to  

The mass absorption coefficients listed in the literature are at particular energies, say Ei,E2, E3. The interpolated value at a specified energy E in between Ej, and E2 is calculated using the following formulae  

Trace analysis permits some simplification of the quantitative models used 

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