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Discusses quenched molecular reorientation and angular momentum for liquids confined to nanopores of silica glasses prepared by the sol-gel process. Natural abundance spin-lattice relaxation times of liquids; Theoretical model for anisotropic molecular reorientation and angular velocity.

An extension of our previous theory of spin relaxation by translational diffusion in two-dimensional (2D) systems is proposed by considering the very nonuniform radial molecular distribution observed at short intermolecular distance. This increases greatly the absolute values of the spin-lattice relaxation rates T-11 and enhances the size effects on their diffusion (or temperature) dependences. The existence of two maxima in these dependences should facilitate the interpretation of experimental data in 2D heterogeneous systems. [ABSTRACT FROM AUTHOR]

Abstract: Diffusion coefficients of water in hydrated cement pastes and mortars obtained from proton field cycling NMR spin lattice relaxation over three orders of magnitude in magnetic field strength are in good agreement with values from molecular dynamics simulations of water on the surface of tobermorite. The level of agreement from these two independent approaches provides mutual support for their validity. [Copyright &y& Elsevier]