Effects of magic-angle spinning on spin-lattice relaxations in talc.

The spin-lattice relaxation times T1 of 1H and 29Si 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. 1H T1 depends on the spinning rate, whereas 29Si T1 is independent of the spinning rate. These facts demonstrate that spin diffusion plays an important role in 1H relaxation but not in 29Si relaxation. 29Si spins relax through dipole-dipole interactions with electron spins directly, which mechanism is not affected by spinning. The relaxation rates have been analyzed theoretically.