next up previous
Next: DISCUSSION Up: DANES STUDY OF Previous: Kramers-Kronig analysis of the

Polarized XANES and DANES measurements

An important aspect of high-tex2html_wrap_inline2104 superconductor research is the connection between the hole concentration in the tex2html_wrap_inline2106-tex2html_wrap_inline2108 bands, the Cu valence, and the tex2html_wrap_inline2104 of the material. In the tex2html_wrap_inline1946 high-tex2html_wrap_inline2104 superconductors, the Cu(2) bond valence sum has been shown [29] to have the same shape versus tex2html_wrap_inline2116 as tex2html_wrap_inline2104, while the bond valence sum of the Cu(1) chain atoms has a linear dependence on oxygen content and is independent of the material's superconductivity. Polarized XANES measurements have been very useful in studies of new high-tex2html_wrap_inline2104 materials. For example, the 3d valence electronic configuration of the Cu atoms in tex2html_wrap_inline1946 was determined by comparing the XANES features of tex2html_wrap_inline1946 to XANES fingerprints of closely related Cu-O compounds [32]. Since DANES methods provide precise, and very easy, assignments of near-edge features to specific sites, DANES studies should prove useful in site-specific valence determinations of high-tex2html_wrap_inline2104 and other materials. In addition, because the tensor properties of the DANES signals are sensitive to the empty orbital symmetries and occupations, there is considerable interest in applying tensor DANES to make site-specific empty orbital maps [34].