Restricted electron motion in a one-dimensional organic conductor: Pulsed-gradient spin-echo ESR in (fluoroanthene)2PF6

The pulsed-gradient spin-echo electron spin resonance method has been used to measure the restricted diffusion of electrons along fluoranthene channels in the quasi-one-dimensional organic conductor (fluoroanthene${)}_2$ ${\mathrm{PF}}_6$. This type of experiment allows one to measure the echo attenuation both as a function of diffusional observation time Δ and effective scattering wave-vector amplitude q. In these experiments Δ was varied between 10 and 20 μs, while q values of up to 2.5×${10}^4$ ${\mathrm{m}}^{\mathrm{-}1}$ were employed, enabling dynamic spatial resolution on the micron scale. The echo attenuation data are broadly characteristic of one-dimensional electron diffusion within the confines of an ensemble of wells, in which the well dimension l is characterized by a distribution p(l)=ll¯ ${}_{}{}^{\mathrm{-}2}{}_{}{}^{}\exp$(l/l¯). Subtle deviations in this behavior can be modeled both by allowing for relaxation effects at the well boundaries, or by allowing for weak boundary permeability.