Network of characterizing functions for stationary populations

Structure-mobility relations of molecular diffusion in nanoporous materials

Depending on the measuring conditions, pulsed field gradient (PFG) NMR measurements of molecular diffusion in beds of nanoporous particles may provide information about the propagation rate of guest molecules in both the intra- and interparticle spaces, as well as through the interface between them. Recent progress in both PFG NMR instrumentation and computational techniques have initiated studies of novel aspects in each of these areas, which are reviewed in this communication. They concern the possibility of multicomponent diffusion measurements with ultra-high pulsed field gradients, the peculiarities of molecular diffusion in channel networks, the determination of the surface-to-volume ratio of nanoporous particles and the dependence of the tortuosity factor of long-range diffusion on the diffusion mode in the intercrystalline space.

Different time regimes of tracer exchange in single-file systems

A complete description of the time dependence of tracer exchange in single-file systems is given. It is based on the combined application of dynamic Monte Carlo simulations and analytical calculations. Depending on the time elapsed, the tracer exchange is found to have different time scaling related to transport modes of either normal diffusion or single-file diffusion. The mode of single-file diffusion is reproduced by recent tracer exchange experiments conducted by laser-polarized 129Xe NMR spectroscopy.