Spin-lattice relaxation of deuterons at multiaxial reorientation of the XD4 tetrahedron

The influence of anisotropic reorientation of XD4 tetrahedron on spin-latti ce relaxation time T-1 is described in terms of uncorrelated simultaneous j umps about the axes of symmetry. Tetrahedron reorientation is described as a Markovian process with a discrete set of orientational states. The analyt ical expressions of Ti for the considered types of multiaxial reorientation of XD4 are obtained. It is found that the dependence T-1(T) can be charact erized by both one and two minima upon different combinations of C-n axes. Equal sets of rotation axes with different mutual arrangements are demonstr ated to bring about closely coinciding T-1(T) curves. The model is applied to the analysis of the experimental temperature dependence of T-1 of the AI D, anion in LiAlD4 and Bu4NAlD4. (C) 2000 Elsevier Science B.V. All rights reserved.