HYPERFINE SCALAR COUPLING FOR ATTRACTIVE IONS IN PARAMAGNETIC SOLUTIONS - ITS EFFECT ON THE T-1 T-2 RATIO IN NMR RELAXATION/

We report careful measurements of the relaxation times T-1 and T-2 of the phosphorus nucleus on the (CH3P+ ions in varying concentrations of .ON (SO3)(2)(2)- anion free radicals in D2O solutions at 25 degrees C for an NMR frequency v(1) = 81 MHz. The hyperfine scalar coupling bet ween the P-31 nuclei and the free radicals is determined from the freq uency shifts of the resonance lines with respect to their position in the diamagnetic solution, It is shown that this interaction has a negl igible effect on the longitudinal relaxation time T-1, which is govern ed by the magnetic dipolar intermolecular coupling, but significantly contributes to the transverse relaxation time T-2, leading to a ratio, T-1/T-2 congruent to 1.5, in excellent agreement with experiment.