Restricted electron motion in 1D organic conductors: PGSE-ESR in (PE)(2)PF6 and (FA)(2)PF6

The pulsed-gradient spin echo electron spin resonance technique has been us ed to study the restricted motion of the conduction electrons in the one-di mensional organic conductors (PE)(2)PF6 and (FA)(2)PF6. Data were collected as a function of temperature, between room temperature and the Peierls tra nsition temperature. Improved signal-to-noise ratio and reduced eddy curren ts were achieved. Echo attenuation for (PE)(2)PF6 was found to fit a model assuming diffusional motion between scattered, totally reflecting, barriers . The free diffusion constant and average barrier distance were successfull y best fitted simultaneously for all temperatures, and the temperature depe ndence of the diffusion constant was found to scale with the previously mea sured AC conductivity. In contrast, PGSE results for the (FA)(2)PF6 crystal s do not fit the above model, possibly due to the existence of basically di fferent restricting factors. (C) 1999 Elsevier Science S.A. All rights rese rved.