NMR microimaging may be used to observe the effect of molecular diffusion in the vicinity of a thin wire subjected to current pulses. By this means the Pulsed Gradient Spin Echo technique can utilises very large pulsed magnetic field gradients, on order of 100 T/m. The quadratic dependence of gradient amplitude on distance from the wire leads to large dynamic range while the distribution of local gradient vectors makes it possible to images anisotropic diffusion. We demonstrate these properties in measurements on polymer solutions and liquid crystals.
J. Stepi"snik,Violation of the gradient approximation in NMR self-diffusion measurements, Zeitschrift fur Phys. Chem. 190, S. 51-62 (1995).
P.T. Callaghan, J. Stepi"snik, Book of Abstracts of 12th Conference of the International Society of Magnetic Resonance, Sydney, 1995 p. L.10.4.
P.T. Callaghan, J. Stepi"snik, Generalised Analysis of Motion Using Magnetic Field Gradients, in book Advances in Magnetic and Optical Resonance , ed. Waren S. Waren, Academic Press, (1995).
P.T. Callaghan, J. Stepi"snik, Phys. Rev. Letters, 75, 4532 (1995)
Fig.1 :Schematic representation of the experimental cell with the picture of gradient vectors of wire superposed on the equigradient conturs in the right corner together with the NMR microimage of capilar crossection (down-left) showing the distribution of spin echo attenuation in 5% solution of 10^6 dalton poly(ethylene oxifde) in water when current of 1.2 A is applied.