X-RayK-Absorption Fine Structure of Niobium and Copper at Cryogenic Temperatures

The x-ray $K$-absorption fine structure of niobium and copper has been investigated at 300, 77, and 4.2°K to determine the fundamental dependence of fine-structure variations on the Debye temperature and the location of scattering potentials. The increase in the amplitude of the fine-structure fluctuations with a lowering of absorber temperature and the dependence of fine-structure temperature variations on the Debye temperature were found to agree with recent theory. No significant change was found in the energy positions of the fine structure as the temperature of the two absorbers was lowered.