- Abstract We show that the relaxation function of the dipolar order is given by exp [-(t/T 1 da) α] exp (-t/T 1 db) where T 1 da and T 1 db are spin-lattice relaxation times: T 1 da due to direct interaction of a given nuclear spin with paramagnetic centers and T 1 db due to indirect interaction with the paramagnetic centers through neighboring nuclear spins. For a homogeneous distribution of paramagnetic centers and nuclear spins, α= D/6 where D is the sample dimensionality. For an inhomogeneous distribution, the sample is divided into d- dimensional subsystems, each containing one paramagnetic center, yielding α=(D+ d)/6. The dipolar relaxation is measured in fluorinated graphite. Data from this experiment and from CaF 2 doped with Mn 2+ in the literature are consistent with this model.