GRAIN-SIZE DEPENDENCE OF PHOTOCHARGE EFFECT IN SILVER IODOBROMIDE PHOTOGRAPHIC-EMULSIONS

Time-resolved photocharge decay studies have been carried out on chemically sensitized gelatino-Ag(I)Br emulsion coatings with Ag(I)Br grain size as the principal variable. Films were characterized optically and sensitometrically. Variation in both maximum photocharge amplitude and photographic speed (intrinsic) among these films reflects primarily variation in optical absorption characteristics dependent on Ag(I)Br grain size. We observe positive photocharge signals and assign them to photoelectrons; accordingly, more carriers are generated at grain faces away from the exposing light than on directly illuminated faces. Maximum positive photocharge amplitude, normalized for the fraction of incident, light absorbed, correlates with both grain size and photographic speed.