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Rapid site assignments of YBa2Cu3O6.6 XANES features using DANES

The ease with which DANES can be used to assign near-edge features to specific inequivalent sites in YBa2Cu3O6.6 is illustrated in Fig. 10, which compares the DANES signal from three Bragg reflections with the XANES signal. The energy positions of previously identified transitions [31] in the near-edge region were assigned using the extrema of the second energy derivatives of the XANES signal. Since the Kramers-Kronig relation between absorption and scattering is similar to a derivative, the same near-edge features appear as first energy derivatives of the DANES signal. Consequently, Fig. 10 shows the first derivatives of the DANES signals and the second derivative of the XANES signal. Note that the two transitions at 4.6 and 10.8 eV have minima that correlate with the sign of the Cu(1) site contribution, indicating these two features are dominated by Cu(1) site contributions. The two features at 17.0 and 24.0 eV have maxima or minima that correlate with the sign of the net Cu contribution, i.e., with the sign of tex2html_wrap_inline2068, and therefore have contributions from both sites. These DANES assignments are consistent with the assignments based on polarized XANES, but are extremely simple compared to the XANES work since the sign of the first energy derivative of the DANES signals is sufficient to make the assignments.