The field dependence of 𝑅 1𝑀 and 𝑅 1𝑝 , shown in Fig. , is thus characterized by two Lorentzian dispersions separated by a factor 658.2 and centred at the proton Larmor frequencies (2𝜋658.2𝜏 𝑐 ) -1 and (2𝜋𝜏 𝑐 ) -1 . Depending on the value of the field dependent 𝜏 𝑒 with respect to those of the field independent 𝜏 𝑟 and 𝜏 𝑀 , the correlation time 𝜏 𝑐 can increase with increasing the magnetic field or can be field independent (for S = 1/2 systems, 𝜏 𝑐 is always field independent). When 𝜏 𝑐 is field dependent, a peak appears in the relaxation profile due to the increase in 𝜏 𝑒 due to the 𝜔 𝑆 𝜏 𝑣 dispersion, and the subsequent decrease due to the 𝜔 𝐼 𝜏 𝑐 dispersion. These equations were derived under a number of approximations, among which the absence of static zero-field splitting and hyperfine coupling between the electron magnetic moment and the magnetic moment of the paramagnetic metal nucleus. These effects can drastically modify the values and the field dependence of the relaxation rates, especially at low fields, An additional contribution to the paramagnetic enhancement is provided by water molecules freely diffusing around the paramagnetic moiety up to a distance of closest approach d. According to the hard-sphere spherical model, the modulation of the dipole-dipole interaction between the unpaired electron(s) and the diffusing water protons provides a translational diffusion contribution, given by