DIFFUSION AND RELAXATION IN INTERFACE LAYERS OF CRYSTALS IN NANOPOROUS GLASS

Below the freezing point, experimental data provide evidence for the e xistence of a non-frozen interface layer (NFL) between the crystal in the pore and the pore walls. The molecules in this layer are effective ly confined in a quasi-two-dimensional space that forces them to reori ent when moving along the curved pore surface. Through this relaxation mechanism, the translational mobility in the unfrozen phase reveals i tself in a pronounced frequency dependence of the spin-lattice relaxat ion time. The experimentally observed drop of the self-diffusion coeff icients by more than one order of magnitude below the phase transition can be interpreted in terms of geometric restrictions as well as inte ractions with the surface. (C) 1998 Elsevier Science Inc.