Anomalous Molecular Dynamics in Confined Spaces

Valiullin, Rustem; Kärger, Jörg

doi:10.1002/9783527622979.ch18

Cited by 2 publications

(1 citation statement)

References 72 publications

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“…By superimposing, over two short time intervals, an additional magnetic field with a large gradient, the displacement of the nuclei (and hence of the molecules in which they are contained) in the time span between these two "gradient pulses" is recorded in a phase shift of their orientation in the plane perpendicular to the magnetic field with respect to the mean orientation. Hence, the distribution of the diffusion path lengths appears in the distribution of these phase shifts and, consequently, in the vector sum of the magnetic moments of the individual spins, i.e., in the magnetization [2,[20][21][22]. Since it is this magnetization which is recorded as the NMR signal, molecular diffusion leads to an attenuation of the signal intensity during the PFG NMR experiments which is the larger the larger the displacements in the time interval between these two gradient pulses are.…”

Section: Signal Attenuation and Distribution Of Diffusivitiesmentioning

confidence: 99%

How to compare diffusion processes assessed by single-particle tracking and pulsed field gradient nuclear magnetic resonance

Bauer

Valiullin

Radons

et al. 2011

The Journal of Chemical Physics

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Heterogeneous diffusion processes occur in many different fields such as transport in living cells or diffusion in porous media. A characterization of the transport parameters of such processes can be achieved by ensemble-based methods, such as pulsed field gradient nuclear magnetic resonance (PFG NMR), or by trajectory-based methods obtained from single-particle tracking (SPT) experiments. In this paper, we study the general relationship between both methods and its application to heterogeneous systems. We derive analytical expressions for the distribution of diffusivities from SPT and further relate it to NMR spin-echo diffusion attenuation functions. To exemplify the applicability of this approach, we employ a well-established two-region exchange model, which has widely been used in the context of PFG NMR studies of multiphase systems subjected to interphase molecular exchange processes. This type of systems, which can also describe a layered liquid with layer-dependent self-diffusion coefficients, has also recently gained attention in SPT experiments. We reformulate the results of the two-region exchange model in terms of SPT-observables and compare its predictions to that obtained using the exact transformation which we derived.

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Section: Signal Attenuation and Distribution Of Diffusivitiesmentioning

confidence: 99%