13C and 1H spin-lattice relaxation in amorphous hydrogenated carbon

The temperature dependences of the C-13 and H-1 magnetization recovery and spin-lattice relaxation times have been measured in amorphous hydrogenated carbon (a-C : H). The observed short and nearly temperature independent proton and C-13 spin-lattice relaxation times demonstrate that the dominant spin-lattice relaxation mechanism is spin diffusion to paramagnetic impurities. The fact that the magnetization recovery curves clearly deviate from the single exponential form demonstrates that the paramagnetic centers aggregate in clusters so that the unpaired electron distribution in a-C:H is strongly inhomogeneous. (C) 1998 Elsevier Science Ltd. All rights reserved.