The origin of the non-exponential relaxation of silver ions in the crystalline ion conductor Ag7P3S11 was analyzed by comparing appropriate 2-time and 3-time 109Ag nuclear magnetic resonance correlation functions. The non-exponentiality was due to a rate distribution, i.e., dynamic heterogeneities, rather than to an intrinsic non-exponentiality. Thus, the data give no evidence for the relevance of correlated back-and-forth jumps on the time scale of the silver relaxation. Further, four-time 109Ag nuclear magnetic resonance correlation functions indicated exchange processes between fast and slow Ag ions that take place on the time scale of the silver jumps and, hence, the dynamic heterogeneities were short lived.

Origin of Non-Exponential Relaxation in a Crystalline Ionic Conductor - a Multidimensional 109Ag NMR Study. M.Vogel, C.Brinkmann, H.Eckert, A.Heuer: Physical Review B, 2004, 69[9], 094302 (5pp)