FLASH-PHOTOLYSIS STUDY OF DYE POSITIVE HOLES IN SPECTRALLY SENSITIZEDEMULSIONS

Spectroscopic properties and kinetic behavior of dye positive holes or iginating From imida-, oxa- and thiacarbocyanines adsorbed to AgBr gra ins were studied by flash photolysis. Dye positive holes produced on f lash irradiation of dyed emulsions within both the absorption band of a dye in the visible and intrinsic absorption of AgBr in the UV region are mostly accompanied by the reversible bleaching of the dye ground absorption and by the appearance of a new absorption in the visible wh ich is partly transient in character. The observed spectral changes ar e due to the production of both, silver aggregates Ag-n(0), and dye po sitive holes. The ability of sensitizing dyes in the excited state for the electron transfer as well as the pathways of dye positive hole tr apping are discussed.