Soliton, Polaron, Phonons in Polyacetylene and Their Interactions

Abstract

Dynamical properties of solitons in trans-polyacetylene have attracted much interest recently. They have been studied mainly by three types of experiments. Electron spin resonance experiments have measured temperature dependences of the halfwidth at the half-maximum and the electron-lattice relaxation rate. The second type has been the dynamic nuclear polarization experiment. It has measured NMR enhancement by pumping microwave power near the electronic Larmor frequency. As the magnetic field is swept through the ESR line, we can see a symmetric pattern if unpaired spins are mobile (Overhauser effect), or an asymmetric pattern if they are immobile (solid state effect). The third type has been the NMR, particularly, the temperature and field dependences of the spin-lattice relaxation time. Although there have been many discussions about the observed results, it would seem agreed upon that there are mobile unpaired spins and that they are more mobile at higher temperatures. It is concluded by motional narrowing of the ESR line shape and the Overhauser effect.