Measurement of translational molecular diffusion using ultrahigh magnetic field gradient NMR

Nuclear magnetic resonance field gradient methods provide a powerful tool with which to study translational molecular diffusion. Techniques described use the huge static Held gradients available in the stray field of superconducting magnets or in specially designed anti-Helmholtz magnets. The experimental concepts and the dynamical ranges of these methods are discussed in detail and carefully compared with established pulsed-field gradient methods. Large-magnitude static Held gradients combined with short radiofrequency-pulse spacings give access to very small diffusion coefficients (down to 10(-15),2 s(-1)) and a high spatial resolution (molecular displacements down to 10 nm). The advantages of static field gradient techniques are demonstrated with several experimental applications selected from the fields of polymer physics, supercooled melts, and biomedical research. (C) 1998 John Wiley & Sons, Inc.