EFFECTS OF MAGIC-ANGLE-SPINNING ON SPIN-LATTICE RELAXATIONS IN TALC

The spin-lattice relaxation times T1 of H-1 and Si-29 spins in talc have been measured at room temperature with and without magic-angle spinning (MAS) of the sample. Paramagnetic impurities work as relaxation centers. H-1 T1 depends on the spinning rate, whereas Si-29 T1 is independent of the spinning rate. These facts demonstrate that spin diffusion plays an important role in H-1 relaxation but not in Si-29 relaxation. Si-29 spins relax through dipole-dipole interactions with electron spins directly, which mechanism is not affected by spinning. The relaxation rates have been analyzed theoretically.