The Overhauser effect

Abstract

In some substances such as metals, semiconductors, paramagnetic solutions, the main mechanism of relaxation for the nuclear spins results from their coupling with unpaired electronic spins in fast relative motion with respect to them. The electronic spins will be those of conduction electrons in metals or semiconductors, of free radical or paramagnetic ions in paramagnetic solutions. The thermal reservoir or ‘lattice’ which provides or takes up the energy required for simultaneous electron-nucleus flips caused by the relaxation, is the kinetic energy of their relative motion.