Debye–Waller factor and anomalous absorption (Ge: 293–5°K)

Experiments measuring the intensity of three reflexions from a `very thick' Ge crystal (Laue case) were made, while the temperature of the crystal was lowered from 293 to 5°K. The variation of the intensity agreed with the dynamic theory, when the Debye temperature Θ, used for the evaluation of the Debye–Waller factor, was assumed to be 290°K throughout the temperature range. This result may suffer some slight correction in the future, but there is no variation of Θ at 20°K. Θ = constant constrasts with the specific heat data of Θ but essentially agrees with Batterman & Chipmans's prediction.