Deep inner-shell experiments

The last two result in damping terms, while the interatom separation can be determined very accurately, essentially by a Fourier transform of the oscillatory part of the pattern. Although there may be very little atomic structure in the continuum, it cannot be completely neglected. There is one situation in which care is needed in the interpretation doubly-excited configurations may extend far into the continuum above an inner-shell threshold and may coincide in energy with EXAFS for some atoms. They are then not easily separated from each other, which may become a source of error in the interpretation. 

For very deep inner shells, an interesting situation arises, where pure atomic physics experiments can actually be better performed on the solid very deep shells have a very small excitation cross section, because their effective radius is so small. This difficulty can be overcome by an enormous increase in the density of absorbers, i.e. by using thin metallic films. Another advantage of this approach is that absolute cross sections are then easily measured, merely by determining the absorption coefficients and weighing the sample, from which its density can be determined much more accurately than for atomic vapours. 

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