Cross-section for resonant reabsorption

This is often written as / = e . The factor W is sometimes loosely called the Debye-Waller factor though it might be better in this context to call it the Lamb-Mossbauer factor. 

The Debye-Waller factor was originally derived during the development of Bragg X-ray scattering theory. The difference between the two effects is that X-ray scattering is fast when compared with the characteristic time for lattice vibrations whereas the mean lifetime of a Mossbauer nucleus is long when compared with the lattice time. 

From equation 1.15 IF is proportional to T at high temperatures. Experience shows that experimentally this is usually not the case because of anhar-monicity of the lattice vibrations. The effects of anharmonicity have been discussed at length by Boyle and Hall [7] and will be met again in connection with the intensities of individual lines in hyperfine interactions. 

We have described the mechanism by which a y-ray can be emitted without recoil and the same arguments apply to resonant reabsorption. Since Mossbauer experiments usually utilise the recoilless emission of y-rays by a 

The resonant absorption cross-section a(E) can be similarly expressed as 

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