The sample was a 25 mm diameter 2000Å thick Cu(111) film grown epitaxially by vapor deposition onto freshly cleaved mica. The c-axis mosaic spread of the film was about FWHM, making it relatively easy to track the Bragg peak versus energy. A thin sample was chosen to minimize the effects of sample x-ray absorption. The diffracted intensities at 8500 eV, about 500 eV below the edge, were photons per second for the Cu(111) Bragg reflection and photons per second for the Cu(222) reflection. Relative to the incident intensity, the diffracted intensities were and for these two Bragg reflections, and the diffracted intensities were well described by the kinematic approximation.
The measured intensities versus energy for the Cu(111) and Cu(222) Bragg reflections are shown in Fig. 5a together with the corresponding fluorescence XAFS signal for comparison. The cusp in the Bragg intensity drops at the edge energy, eV, to about of the pre-edge intensity at 8500 eV for the Cu(111) reflection and to about for the Cu(222) reflection. This difference in the relative cusp drop between the two reflections is caused by the decrease in with . The fine structure oscillations above the absorption edge are present in both the DAFS and XAFS signals and have similar sizes, peak-to-peak, when normalized to their corresponding cusp drop or edge step sizes.