Long-time behaviour of spin coherences in solids

The long-time behaviour (t greater than or equal to 1 ms) of dipolar couple d nuclear spin systems, highlighted by the high resolution nuclear magnetic resonance (NMR) spectra of abundant nuclei in rigid solids, is explained s atisfactorily as a manifestation in NMR of the famous 'long-time tail effec t'. The time dependence of the transverse magnetization at the long-time li mit, which is fundamentally different from the initial exponential decay, i s closely related to the dimension of the spin network embedded in real spa ce, opening a new approach to measuring the fractal dimension of coupled sp ins in solids.