Detection of Two Types of Reduction-Sensitization Centers by Microwave Photoconductivity Measurement

Abstract

A cubic bromide emulsion was reduction sensitized at pAgs 5.6 and 7.3 and an octahedral silver bromide emulsion at pAg 8.9. The sensitizer used was SnCl₂·2H₂O. The sensitized cubic microcrystals showed an increase in microwave photoconductivity (MPC) at both pAgs while MPC decreased insensitized octahedral microcrystals. For the cubic microcrystals at pAg 7.3 the MPC increased with increasing sensitizer concentration until just before the appearance of fog. At pAg 5.6, however, MPC did not increase with increasing sensitizer concentration. With the octahedral microcrystals, increasing sensitizer concentration resulted in a corespondingly lower MPC. In both the cubic and octahedral emulsions, once fog appeared, MPC decreased to a lower value than in the unsensitized emulsion. These results are considered to be direct evidence for the production of both electron traps and hole traps by reduction sensitization.