Spectral Sensitization and Supersensitization

Abstract

AbstractA theory of spectral sensitization and supersensitization is presented. According to this photoaggregation theory, over the toe and linear segments of the characteristic curve, dye and supersensitizer excitations decay by Auger processes at Ag2, Ag20, Ag2S or (Ag,Au)S sensitizing donor centres, the energy released by combination of the donor electron and the exciton hole is carried away as kinetic energy by the exciton electron in a state of the conduction band. Back-electron transfer is prevented by the rapid dissociation of the remaining Ag2+, Ag20+, AgS+ or (Ag,Au)S+ centre with passage of an /4g+ or Au+ ion into an interstitial position. Over the wavelength range between 400 nm (3.1 eV) and 1,200 nm (1 eV), the latent image is formed by the photoaggregation of Ag and Au atoms equivalent to sensitizing donor molecules to give Agf, AuAgf, Att2Agf or larger acceptor centres. The silver halide crystal does not undergo photolysis but acts as a carrier for the sensitizing molecules and as a transpor...