NEW PERSPECTIVES OF NMR IN ULTRAHIGH STATIC MAGNETIC-FIELD GRADIENTS

The magnetic field gradient nuclear magnetic resonance (NMR) stimulated echo experiment measures the incoherent (or self) part of the intermediate scattering function S(Q, t) similar to [exp[ -iQr(0)] exp [iQr(t)]] with a 'generalized' scattering vector Q = gamma.g.tau (gamma is the gyromagnetic ratio, g is the magnetic field gradient, tau is the evolution time). With ultrahigh static field gradients up to approximate to 180 T/m, a prototype of which has recently been installed in Mainz, Q-values up to > 10(-2) Angstrom(-1) become accessible. The first part of the paper focusses on details of this technical development and points out the close analogy with incoherent neutron scattering. In the second part, the enormous new possibilities of this kind of gradient NMR are demonstrated through a collection of most recent applications: the measurement of small self-diffusion coefficients down to about 10(-15) m(2) s(-1) in supercooled liquids and in molecular crystals, long chain polymer dynamics, restricted diffusion in systems of confined mesoscopic geometries and anomalous diffusion on fractal structures.