ESR Study of Silver Clusters in AgCl and AgBr. An Attempt to Detect Photographic Latent Images

ESR signals observed after the bandgap irradiation of AgCl and AgBr sols and primitive emulsions are reported. Their parameters are similar to those of small, pseudo‐metallic silver particles. An assignment to latent images is proposed on the basis of the results of empirical ESR/photographic crossover experiments. The size(s) of the latent image agglomerates seems to vary according to the halide, but there appears to be discrete size or small size distribution for a given system. Although it would appear that the clusters are larger than Ag7, precise particle size deductions from the ESR data are shown to await the development of a suitable electronic theory. Smaller, neutral or charged molecular silver aggregates have not, so far, been detected in pure silver halide systems. However, it is possible that signals are present but are too dispersed through a large field range for detection. The existing ESR data for silver clusters are reviewed and reviewed and the possible electronic structures and associated magnetic properties of latent images are discussed.