Position effect of Ag₂ doped in cubic silver bromide emulsions

In the emulsifying process of silver bromide microcrystals in the double-jet apparatus controlled by a microcomputer, a specific quantity of DMAB was added at different time when the crystal growth to obtain a series of cubic AgBr emulsions in which Ag₂ were doped into different depths of AgBr microcrystals. The results from determination of photographic properties of these emulsions showed: 1) that the sensitivities of Ag₂ doped emulsions, relative to that of the undoped emulsion as the controlled one, were remarkably increased; 2) that a significant cooperative sensitization of the internal doped silver dimmers with the surface sulfur-plus-gold and dye sensitizations was observed; 3) that the closer to the surface of grains the Ag₂ doped in AgBr grains was, and the greater the sensitivities of the doped emulsions were; 4) that fog densities of all emulsions doped by Ag₂, including those primitive, sensitized by sulfur-plus-gold and by green-sensitive dye, were kept in a reasonably low level.