PHOTOGRAPHICAL AND UV-VIS SPECTROSCOPICAL INVESTIGATIONS OF LIGAND PROTECTED SILVER CLUSTERS IN ULTRA-FINE GRAINED AGBR AND AGBR I EMULSIONLAYERS/

Various emulsion layers with different photographic sensitivities were produced from ultra fine grained silver-halide-gelatin-emulsions chem ically sensitized in four different ways (I.: without chemical sensiti zers, II: sulfur sensitized, III: gold sensitized, IV: sulfur+gold sen sitized). The different sensitivities were compared with the different W-VIS-spectra of photo induced silver clusters formed by exposure of the Various emulsion layers to flash light. The UV-VIS-spectra display ed absorption bands at about 340nm (oligomeric silver clusters with 5 silver atoms), 390 nm (plasmon polaritons of 4 nm silver clusters surr ounded by Ag+ ions), 470 nm, 530 nm and 630 nm. The absorption range b etween 420nm and 700 nm may be attributed to silver clusters with diam eters about 4 nm, too. When these clusters are embedded within the int erface ''gelatin/silver halide'', or within silver bromide, absorption maxima at 470 nm, or 530 to 540 nm, respectively may occur. The 630 n m band may occur, when the cluster concentration within the interface ''gelatin/silver halide'' becomes so large that the clusters are allow ed to approach each other to distances less than one particle diameter . Sensitivity gains, above all, run parallel with remarkable red shift ings of the 630 nm absorption maximum. The gold sensitization has rema rkably influenced the 630 nm band.