Abstract: Electron-nuclear dipolar interaction and spin-diffusion play very important roles in the relaxation processes of molecules adsorbed on solids containing surface eleetrons, such aS charcoal,alumina and silica gel.According to this relaxation rnechanism,the relation between spin-lattice relaxation time(T_1e)and correlation tim-(τ_c)was obtainted:T_1e,-k(τ_c/1+ω₀²τ_c²)^1/2,k is a con-stant for a given solid. It was found that the relaxations of toluene adsorbed on silica gel were interpretted well by this formula, The correlation times at dirrerent temperatures and the activqtion energy(E_a=15.0kJ/mol) of methyl group in toluene adsorbed on silica gel were obtained.The correlation times are in the range of 3.56×10^-9-5.76×10^-8s during 374 K and 240 K.

Key words: NMR phpsisorption, Longitudinal relaxation, Spin dirrusion