Spin-lattice relaxation of the solitonic defect in isotopically substituted trans-polyacetylene

Abstract

We have measured the spin-lattice relaxation rates, R{sub 1}, for the spin of the electron defect in pristine trans-polyacetylene (t-PA) as a function of temperature for the isotopic forms (CD){sub x}, ({sup 13}CD){sub x}, (CH){sub x}, and ({sup 13}CH){sub x}. The data have been compared with the soliton-phonon-based dynamics model of Maki and the localized metal-phonon based dynamics model of Robinson et al. We concluded that the latter model is preferred; it exactly explains the R{sub 1} data for (CD){sub x} and ({sup 13}CD){sub x} t-PA. We find that the R{sub 1} data of the proton-containing forms of t-PA, (CH){sub x} and ({sup 13}CH){sub x}, are complicated by the presence of spin 1/2 nuclei, which are strongly coupled to each other, and which provide an additional dynamic path for defect-spin relaxation.