Rotational Polarization of Molecular Groups in Solids

Abstract

When nuclear spin relaxation in solids is due to rapid random rotational motion of molecular groups, magnetic relaxation parameters are dynamically coupled to populations of molecular rotational states. Relaxation of magnetization induces population differences between clockwise and anticlockwise rotational states (rotational polarization), resulting in nonexponential magnetic relaxation. At low temperature a nonequilibrium population difference between rotational states may be generated by a temperature change, and subsequent relaxation induces magnetic dipolar polarization.