Observation of molecular migration in porous media using 2D exchange spectroscopy in the inhomogeneous magnetic field

Propagator-resolved 2D exchange in porous media in the inhomogeneous magnetic field

“…In this paper, we will look at two different widths, 0.8 FWHM and 1.0 FWHM, the equivalent of 4.3 kHz and 5.2 kHz. This choice is consistent with the compromise between the signal to noise ratio and the sensitivity to exchange as found in reference [9]. The average intensities at these offsets are plotted in Fig.…”

“…In a previous paper [9] we demonstrated a 2D exchange technique to investigate molecular motion through a porous media in an inhomogeneous magnetic field. We explored the molecular motion of water molecules through two sizes of monodisperse glass bead packs.…”

“…The ability to access the spatial information therefore provides a more robust check on any model used to interpret our experimental results. It is this use of a well-defined spatial dimension which differentiates our method from earlier local field exchange methods such as DDIF or the 2D method described in reference [9].…”

Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments

“…Techniques often used such as diffusion tensor imaging 9 can characterize the anisotropy present when pores are coherently placed within the specimen, 10 while multiple diffusion time experiments can, to a certain extent, characterize the tortuosity and surface to volume ratio 5,11,12 and fractal dimensions 13 of the specimen. Other diffusionbased methods exist to quantify flow phenomena, [14][15][16][17] the internal magnetic field of the samples, [18][19][20] and to a certain extent, exchange properties 21,22 of the porous media. The q-space approach 1,23 introduced yet another important quantifiable microstructural parameter which characterizes the pores: their average size, which is important in most diffusion NMR applications such as emulsions 24 and central nervous system tissues.…”

Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

“…As an alternative to sophisticated hardware one can use the field inhomogeneities generated by magnetic susceptibility differences of the hydrated porous medium itself [20]. Callaghan and co-workers successfully exploited the field inhomogeneity to observe molecular migration of water molecules by means of 2D Fourier exchange spectroscopy [21] and later added a propagator dimension for spatial localization [22].…”