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

Time-resolved photocharge decay studies have been carried out on chemi cally sensitized gelatino-Ag(I)Br emulsion coatings with Ag(I)Br grain size as the principal variable. Films were characterized optically an d sensitometrically. Variation in both maximum photocharge amplitude a nd 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 fac es away from the exposing light than on directly illuminated faces. Ma ximum positive photocharge amplitude, normalized for the fraction of i ncident, light absorbed, correlates with both grain size and photograp hic speed.