Proton NMR in the organic conductor tetramethyltetraselenafulvalinium hexafluorophosphate

Proton NMR measurements have been made on ${\mathrm{}\left(\mathrm{TMTSF}\right)\mathrm{}}_2$P${\mathrm{F}}_6$ (di-tetramethyltetraselenafuvalene P${\mathrm{F}}_6$) at 10 MHz. The linewidth increases below the metal-insulator transition. $T_{\mathrm{MI}}$, indicating the onset of inhomogeneous local fields associated with the appearance of a spin-density wave. The spin-lattice relaxation time $T_1$ increases steeply below $T_{\mathrm{MI}}$. Two minima in $T_1$, at 18 and 60 K, are tentatively associated with changes in the molecular dynamics.