Comment on the intermolecular relaxation dispersion at 400, 600, 800 MHz of the (CH3)4N+ protons in D2O solutions with paramagnetic [Gd(D2O)8]3+ complexes

New high-field proton relaxation measurements are satisfactorily interpreted without any adjustable parameter by a theoretical model based on the Solomon relaxation formalism and on the relative translational Brownian diffusion of the cation pair. Thus, at least in this frequency range, the longitudinal electron relaxation times of Gd3+ are much longer than the translational correlation time of the interionic diffusion, in agreement with the EPR studies of Merbachʹs group (Helv. Chim. Acta 76 (1993) 2129), but in contradiction with Dinesenʹs and Bryantʹs conclusion (Chem. Phys. Lett. 303 (1999) 187).