[en] The results of the studies of some specific features of the relaxation of spins ''tied'' to impurity atoms in nonmagnetic dielectrics are reported. The spin relaxation takes place due to a thermal modulation of the reciprocal distances between isolated impurities and neighbouring matrix atoms. The treatment is based on the assumption that the equilibrium position of an impurity is the inversion center. It is in this case that taking into account the alteration of force constants is followed by a number of qualitative modifications in the behaviour of field and temperature dependence of impurity spin relaxation rate