Abstract
We have characterized the electronic structure of single crystals of the organic quasi-one-dimensional salt (TMTTF)2ReO4 (TMTTF=tetramethyl-tetrathiafulvalene) by x-ray-absorption near-edge spectroscopy and x-ray photoemission spectroscopy using synchrotron radiation under low-intensity conditions (single-bunch ring operation mode) in order to strongly reduce detrimental beam-induced damage. The observed differences in spectra taken at T=116 K and T=207 K are ascribed to the anion-ordering transition, which takes place at 155 K. It is proposed that the ordering transition driven by the anions perturbs the structural organization of the organic stacks, increasing the overlap of the -type orbitals through dimerization