Abstract: A series of cubic AgBrⅠ core-AgBr shell emulsions with different amounts of DMAB used for producing Ag₂ (R center) in the core were prepared by using a double-jet apparatus controlled by a microcomputer.The results from sensitometric measurements of these emulsions show that the emulsions doped by Ag₂ in the AgBrⅠ core exhibited a significant increase in sensitivities and the existence of I^- in the core-shell grains did not influence the sensitization of the internal Ag₂; and that these core-shell emulsions after surface sensitization by sulfur-plus-gold exhibited a remarkable cooperative sensitization,i.e.their sensitivities were much higher than that of the controlled one which was not doped with Ag₂ in the core.These results reconfirmed two kinds of different sensitization mechanisms,i.e.via trapping holes by the internal Ag₂ centers and concentration of electrons by sulfur-plus-gold sensitizing centers.Taking advantage to both mechanisms,a cooperative sensitization could be realized to improve the efficiency of latent image formation.

Key words: hole-electron converter, AgBrⅠ core-shell emulsion, doped by Ag dimmer, sulfur-plus-gold sensitization, cooperative sensitization