NMR RELAXATION AND MOLECULAR-REORIENTATION OVER UNEQUAL POTENTIAL BARRIERS

Modulation of the dipolar Hamiltonian owing to complex motion of the internuclear vector which undergoes an isotropic overall motion associated with jumps between two or three potential minima of various shapes has been considered, and general equations describing nuclear magnetic relaxation have been derived. The calculations take into account the change in the internuclear vector length during the internal motion. If changes in the internuclear vector take place, internal motion of a frequency lower than the frequency of the overall motion can affect the relaxation rate significantly. There is evidence of splitting of the minimum of the function In T-1 versus the inverse of the temperature due to two modes of motion between three inequivalent minima.