In 1950, Erwin Hahn pointed out that spin echoes in Nuclear Magnetic Resonance (NMR) could be used to measure molecular translational motion, an effect made possible because nuclear spins carry a phase determined by the history of their residence in magnetic fields. If, through our own volition or by consequence of sample structure, magnetic fields can be given some spatial variation, and if the spin-bearing molecules translate, then the spin phases can be made to tell the story of that migration. Unlike modern bio-molecular NMR, the multitude of tricks used to measure molecular translational ... More

In 1950, Erwin Hahn pointed out that spin echoes in Nuclear Magnetic Resonance (NMR) could be used to measure molecular translational motion, an effect made possible because nuclear spins carry a phase determined by the history of their residence in magnetic fields. If, through our own volition or by consequence of sample structure, magnetic fields can be given some spatial variation, and if the spin-bearing molecules translate, then the spin phases can be made to tell the story of that migration. Unlike modern bio-molecular NMR, the multitude of tricks used to measure molecular translational motion take place without the need for high spectral resolution. They work, with equal power, at low field and in the absence of spectral discrimination, and so lend themselves to that new branch of NMR technology that concerns itself with ‘outside the laboratory’ applications, in geophysics and petroleum physics, in horticulture, in food technology, in security screening and in environmental monitoring. The translational dynamics of molecules provide a signature for molecular size and shape size, the visco-elasticity of the surrounding fluid medium, their organization into supramolecular assemblies, their exchange between different sites, their intermittent binding, their confinement by a surrounding matrix or phase boundary, and the topology of that confinement. This book takes us through the various underlying principles of molecular translational dynamics, outlining the ways in which magnetic resonance, through the use of magnetic field gradients, can reveal those dynamics. It covers the full range of time and Frequency Domain methodologies, showing how they can be used, as well as advances in ‘scattering and diffraction’ methods, multidimensional exchange and correlation experiments, and orientational correlation methods ideal for studying dynamics in anisotropic environments.