1 research outputs found
Near-Edge X‑ray Absorption Fine Structure Investigation of the Quasi-One-Dimensional Organic Conductor (TMTSF)<sub>2</sub>PF<sub>6</sub>
We present high-resolution
near-edge X-ray absorption fine structure
(NEXAFS) measurements at the P L<sub>2/3</sub> edges, F K edge, C
K edge, and Se M<sub>2/3</sub> edges of the quasi-one-dimensional
(1D) conductor and superconductor (TMTSF)<sub>2</sub>PF<sub>6</sub>. NEXAFS allows probing the donor and acceptor moieties separately;
spectra were recorded between room temperature (RT) and 30 K at normal
incidence. Spectra taken around RT were also studied as a function
of the angle (θ) between the electric field of the X-ray beam
and the 1D conducting direction. In contrast with a previous study
of the S L<sub>2/3</sub>-edges spectra in (TMTTF)<sub>2</sub>AsF<sub>6</sub>, the Se M<sub>2/3</sub> edges of (TMTSF)<sub>2</sub>PF<sub>6</sub> do not exhibit a well-resolved spectrum. Surprisingly, the
C K-edge spectra contain three well-defined peaks exhibiting strong
and nontrivial θ and temperature dependence. The nature of these
peaks as well as those of the F K-edge spectra could be rationalized
on the basis of first-principles DFT calculations. Despite the structural
similarity, the NEXAFS spectra of (TMTSF)<sub>2</sub>PF<sub>6</sub> and (TMTTF)<sub>2</sub>AsF<sub>6</sub> exhibit important differences.
In contrast with the case of (TMTTF)<sub>2</sub>AsF<sub>6</sub>, the
F K-edge spectra of (TMTSF)<sub>2</sub>PF<sub>6</sub> do not change
with temperature despite stronger donor–anion interactions.
All these features reveal subtle differences in the electronic structure
of the TMTSF and TMTTF families of salts