Electrical Measurements on Photographic Grains Containing Cadmium

Abstract

Ionic conductance and electron lifetime measurements have been made on emulsion grains containing cadmium. The reduction in the concentration of interstitial silver ions because of the divalent cationic impurity, decreases the ionic conductivity, correspondingly increases the electron lifetimes in the grains, and introduces a high-intensity, reciprocity-law failure in the emulsion. These results confirm the conclusion that silver ions are the dominant carriers of ionic current and that these same silver ions play a major role in the initial trapping of photoelectrons during latent-image formation. Moreover, they strongly suggest that the silver ions responsible for ionic conductance in grains with no impurity additions are interstitials generated at kink sites on the grain surface and moving in a space-change layer within the grains.