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Edit: Fluoresence due to the continuum emitted by the substrate (or overlying material) can also contribute to phi(rho*z) within the thin layer of interest, and this (depending on beam energy) could be more significant for Zn Ka than for the Ka lines of elements of lower atomic number. I believe that this is what Armstrong is hinting at near the bottom of p. 278 in EPQ, where he states, "...phi(rho*z) equations probably inadvertently incorporate some correction for continuum fluorescence." Heinrich also makes brief mention of this effect in section 10.2.1 of "Electron Beam X-ray Microanalysis."

This is an excellent addition to CalcZAF. We will use it at Lehigh 2018.Inspection of the equations used for the prz curve do show that it is a function of composition via the backscatter fraction and overvoltage parameters, and those are weighted by concentration; so yes, the curves are specific to the composition. As well the emitted curve clearly depends on the mac of the matrix material, again weighted by concentration.My understanding is that the monte carlo simulation is superior for determining the lateral and vertical limits of electron scattering compared to the prz algorithm which is based on a small number of tracer experiments and via curve fitting generalized to all compositions. That is, the MC calculation is truly composition specific.One problem with defining the depth of the analytical volume is that it is a cumulative distribution function. Is the depth the limit of electron scattering at zero residual energy, or the 99.99% limit of characteristic X-ray production, or emission. These are all quite different. There are cumulative plots in the older versions of Goldstein that allow you to quote the resolution at a specific percentage of total. The contoured energy deposition plot of Casino is very nice in outlining the volume from which a given X-ray energy can be generated.

One problem with defining the depth of the analytical volume is that it is a cumulative distribution function. Is the depth the limit of electron scattering at zero residual energy, or the 99.99% limit of characteristic X-ray production, or emission. These are all quite different. There are cumulative plots in the older versions of Goldstein that allow you to quote the resolution at a specific percentage of total. The contoured energy deposition plot of Casino is very nice in outlining the volume from which a given X-ray energy can be generated.