Formation and Properties of Sub-Image and Latent-Image Silver Specks Part IlI: Properties of Silver Sub-Specks Produced by Radiation

Sub-image specks have been produced in monodisperse AgBr emulsions by a weak pre-exposure with y-rays, with electrons, and with light at 77 K as well as at room temperature. Coverage of the pre-exposed grains by precipitation of additional AgBr onto the grains or oxidation of the sub-specks at the crystal surfaces led to emulsions which now contained the sub-specks only in the interior of the grains. Upon an image-wise second exposure and surface development all these emulsions showed an increase of the sensitivity in the threshold region of the characteristic curve which can be explained only by an over-all increase of the quantum yield due to capture of holes by the sub-specks. These sub-specks consequently are not precursors of latent image specks and they do not influence latent image topography.Under certain conditions in addition to the former another type of sub-specks (presumably larger in size but still nondevelopable) can be found which do influence latent image topography, which, hence, act as electron traps and which upon second exposure can grow to latent image specks. The experimental results clearly show that sub-specks produced by radiation exhibit exactly the same properties as those obtained by chemical reduction.