1998 Volume 61 Issue 6 Pages 372-383
Mono-dispersed cubo-octahedral silver bromide grains were digested with three different sulfur sensitizers, and crystal-face selectivity of latent image centers was determined by means of arrested development. Under the condition of low-intensity exposure, latent image centers were formed entirely on {111} face of moderately digested grains with all the sulfur sensitizers examined. Under optimum and over-digested condition, the grains sensitized with sodium thiosulfate had latent image centers on their {111} face, while those sensitized with triethyl thiourea and 3-ethyl-5-benzylidene rhodanine had latent image centers preferentially on their {100} face. It was discovered that the crystal-face selectivity of the location of latent image centers was affected by the kind of sulfur sensitizers and degree of digestion for sulfur sensitization. The amount of silver sulfide formed was measured by use of radio-active 35S-labeled sensitizers. Desensitization caused by cyanine dyes on cubo-octahedral AgBr grains was much weaker when latent image centers were formed on {100} face than on {111} face. The above-stated observations lead to the proposal of the following mechanism. The formation of effective sulfur sensitization centers from silver sulfide is faster on {111} face than on {100} face. However, a sulfur sensitization center on {100} face acts more effectively than that on {111} face for competition of latent image formation.
