Electron and nuclear spin relaxation in paramagnetic transition-metal complexes with S = 1. The effects of a non-zero average zero-field splitting on the spin energy levels

The effects of a non-zero average zero-field splitting on electron spin relaxation in paramagnetic (S = 1) complexes is treated theoretically. The spin-lattice interaction is postulated to be a simple scalar P(t). S process with correlation time Ti. This process is assumed not to modulate the zero-field splitting which, however, is modulated by the molecular tumbling. The frequency dependence of the nuclear relaxation time (Tl) now depends on the magnitude of the zero-field splitting constant (D), and, for large values of D, the value of T1 is independent of the applied field strength.