We report the first x-ray-absorption measurements on conducting charge-transfer salts, using synchrotron radiation. By measuring the Se $K\alpha$ x-ray-absorption near-edge structure (XANES) of hexamethylenetetraselenafulvalene ${\mathrm{}\left(\mathrm{HMTSF}\right)\mathrm{}}^0$ and fully charge-transferred HMTSF-tetrafluorotetracyanoquinodimethane (HMTSF-TFTCNQ) and comparing the results with those on partially charge-transferred HMTSF-tetracyanoquinodimethane (HMTSF-TCNQ), we conclude that the charge on the cation stack in the latter is delocalized as opposed to being concentrated on discrete sites of a generalized Wigner lattice.

• Received 14 September 1983

DOI:https://doi.org/10.1103/PhysRevB.30.6973