Evidence for soliton-phonon interaction in trans-polyacetylene: temperature and frequency dependence of electron spin-lattice relaxation data

The temperature, frequency, and isotope dependence of the electron spin-lattice relaxation rate R1 for the paramagnetic defects in pristine trans-polyacetylene is analyzed in terms of a model in which the electron-electron dipolar interaction between spins is modulated by one-dimensional diffusion induced by phonon scattering of the mobile spins. At room temperature, this model predicts a T/sup 1/2/ temperature dependence of R1; at low temperatures, depending upon assumptions about the phonon spectrum estimates on the temperature dependence of R1 range from TS to T/sup 5/2/. The frequency dependence of R1 is theoretically predicted to be described by a omega/sup -1/2/ dependence which is found to accurately fit the experimental data obtained over the frequency range 35 MHz to 40 GHz. The interpretation of electron spin-lattice relaxation data is consistent with ENDOR, electron phase memory relaxation data, EPR line-width data, and nuclear relaxation data. The implications of this analysis are considered for various solution descriptions of the paramagnetic defect. 42 references, 8 figures.