Field dependent spin-lattice relaxation times of nuclear paramagnetic systems at low temperatures

The spin-lattice relaxation time T1 in the vapor and liquid phases of 3He in magnetic fields ranging from 1 to 15 tesla was studied. Results indicate a boundary substrate mediated field dependence of T1 in both phases. It is proposed that this is due to a field dependent coupling of the 3He magnetic moments to paramagnetic impurity centers in the substrate. Theoretical calculations and experiments suggest an anisotropic band structure in the direct gap semiconductor, polycrystalline transpolyacetylene, (CH)/sub x/. A direct consequence is a theory of one-dimensional mobility of electronic spins along molecular chains, which can be quantitatively tested with the field dependence of the spin-lattice relaxation T1 of the protons in polyacetylene. Measurements of T1 down to 2K and in magnetic fields up to 8 tesla, complementing the measurements in lower fields (<2 tesla) by others are reported here