Spatio-temporal anomalous diffusion in heterogeneous media by NMR

For the first time, the diffusion phase diagram in highly confined colloidal systems, predicted by Continuous Time Random Walk (CTRW), is experimentally obtained. Temporal and spatial fractional exponents, $α$ and $μ$, introduced within the framework of CTRW, are simultaneously measured by Pulse Field Gradient Nuclear Magnetic Resonance technique in samples of micro-beads dispersed in water. We find that $α$ depends on the disorder degree of the system. Conversely, $μ$ depends on both bead sizes and magnetic susceptibility differences within samples. Our findings fully match the CTRW predictions.

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