Magnetic Relaxation in Dynamically Heterogeneous Systems

Nuclear magnetic spin-lattice relaxation in dynamically heterogeneous systems is generally coupled; that is, the rapidly moving liquid components do not relax independently of the rotationally immobilized or solid components. The consequences of this coupling are that the generally observable relaxation rates of the liquid components may not be interpreted using the standard theories of liquid spin relaxation, but the coupling also provides a pathway for reading the characteristics of the solid spin system by direct observation of only the liquid spin system. This fact provides a considerable opportunity for magnetic analysis of complex materials in such environments as process control, and also provides completely new opportunities for magnetic imaging. By application of an off-resonance preparation pulse one may impose the spin relaxation characteristics of the solid on the liquid, thereby providing solid component information in the liquid magnetic image.