Sensitometric and spectroscopic techniques are used to study the effect of 4-hydroxy- 6-methyl-1,3,3a,7-tetraazaindene (TAI) during the sulphur sensitization of AgBr octahedra. TAI increased the speed of an oversensitized emulsion, causing it to have a speed comparable with the optimally sulfur-sensitized emulsion at high irradiance. TAI decreased the absorption by sulphide centres at 1.5 mmole concentration but not at 1 mmole. The long wavelength sensitivity (>500 nm) increased at 1 mmole TAI concentration, but decreased at 1.5 mmole TAI concentration, whereas the activation energy for this response was reduced at both TAI levels. These results are interpreted using a model which assumes that TAI interacts with multiple-sulfide centers to lower their ground-state energy level, but not their electron-trapping energy level. This interaction reduces the degree of free-hole/trapped-electron recombination that occurs at these centers. The enhancement of this recombination channel by high levels of sensitizer is what causes the oversensitization effect (Refer to PDF file for exact formulas).

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The authors thank Evan Charlier of the Chemistry Department, University of Antwerp, for the radiotracer data and Christel Geukens of Agfa-Gevaert, Mortsel, for the DRS data.ISSN:1368-2199 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)


RIT – Main Campus