Relaxation dispersion of mobile liquids in inorganic matrices

Relaxation Dispersion of Mobile Liquids in Inorganic Matrices 

An important feature of liquids at surfaces or interfaces is that generally the molecules at the surface are translationally mobile with 

Kimmich and coworkers have studied the magnetic relaxation dispersion of liquids adsorbed on or contained in microporous inorganic materials such as glasses and packed silica (34-43) and analyze the relaxation dispersion data using Levy walk statistics for surface diffusion to build 

Ti oc The observed NMR signal generally decays exponentially, which supports the conclusion that there is rapid material exchange between surface and bulk phases of liquid in the pore. The shift on the frequency axis associated with the freezing event is consistent with the blocking of rapid exchange between bulk and surface phases i.e., elimination of the bulk phase. A similar power law is found for tetradecane in Vycor above the freezing temperature. 

Relaxation dispersion data for water on Cab-O-Sil, which is a monodis-perse silica fine particulate, are shown in Fig. 2 (45). The data are analyzed in terms of the model summarized schematically in Fig. 3. The y process characterizes the high frequency local motions of the liquid in the surface phase and defines the high field relaxation dispersion. There is little field dependence because the local motions are rapid. The p process defines the power-law region of the relaxation dispersion in this model and characterizes the molecular reorientations mediated by translational displacements on the length scale of the order of the monomer size, or the particle size. The a process represents averaging of molecular orientations by translational displacements on the order of the particle cluster size, which is limited to the long time or low frequency end by exchange with bulk or free water. This model has been discussed in a number of contexts and extended studies have been conducted (34,41,43). 

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Relaxation dispersion of mobile liquids in inorganic matrices... 

III. Relaxation Dispersion of Mobile Liquids in Inorganic Matrices... 

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