79Br solid state NMR studies of surfaces, point defects and dislocations in silver halides

Pure and mixed silver halide crystals form the basis of chemical photography. The authors have used 79Br solid state NMR at 4.7 T to characterize the structure and dynamics of defects and surface effects that may be involved in determining the photographic properties of these materials. The influence of free and bound vacancies on bromine spin-lattice relaxation in doped AgBr single crystals and microcrystals was studied and interpreted within the context of the space charge model. Microcrystals subjected to compressive strain have a higher dislocation density as reflected in linewidths and 'missing' Br signal intensity. For crystals under one micron in size, the integrated Br signal intensity is a function of a crystallite size. We have established that the electric field gradient deviates from cubic symmetry within 200 A of the crystal surface. (author). 26 refs.; 4 tabs