Spin Relaxation Processes in a Two-Proton System Undergoing Anisotropic Reorientation

TLDR

The study’s results apply to liquids and solids when the axis tumbling correlation time is much shorter than T2. The authors computed T1 and T2 for two I=½ spins undergoing anisotropic reorientation, showing that the two motions’ relaxation contributions are coupled, that T1 equals T2 in nonviscous liquids, and that the formalism extends to multispin systems.

Abstract

The spin-lattice relaxation time T1 and the spin-spin relaxation time T2 for two identical spins I=½ have been calculated for anisotropic reorientation in which the spin pair reorients randomly about an axis which, in turn, tumbles randomly. The results are applicable to liquids and solids provided that the correlation time for tumbling of the axis is small compared to T2. Although the two types of motion are independent, their contributions to relaxation are not. For nonviscous liquids, T1=T2. The results are generalized to multispin systems.