Silver bromide grains

Fig. 5. Electron micrograph of two silver grains obtained by developing silver bromide grains in a distortionless hydroquinone developer.

Fig. 2. Using the carbon replica technique, this is an electron micrograph of cubic silver bromide grains in which the comers have been slightly rounded due to the presence of a silver complexing agent. (Photo by Dr. Donald h Black, Eastman Kodak Company)...

Amount of Sulfide Needed for Optimum Sensitization, sturmer and Blackburn (128) used radioactive sulfur to measure the concentration of sulfide ions formed on a silver bromide grain surface by thiosulfate. The number at optimum sensitization depended on the exposure irradiance to be used. The number was about 10,000 ions/pm for a high-irradiance exposure and about 20,000 for a medium-irradiance exposure. 

In a second procedure, useful for forming reversal or direct X-ray emulsions, a high concentration of ammonia is used to form a complex precipitate with silver bromide, by mixing ammoniacal silver nitrate and ammoniacal potassium bromide. Dilution with water decomposes the ammonia complex, and silver bromide grains form.9... 

The remarkable effect of a minute trace of sulphur on the surface of a silver bromide grain, referred to in 16, indicates that the instability of a one-dimensional interface may be fundamental to the speed of the modem photographic plate. 

When a camera shutter opens, incoming light energizes the silver bromide grains, causing some of the bromide ions to lose an electron and reduce some of the silver ions to silver atoms. These are called activated grains. 

Photographic emulsions composed of octahedral silver bromide grains were used in these experiments. The average grain size was 0.7 pm, or 0.2 pm. Methanolic solutions of various dyes were added to the emulsions, which were then coated at about 40 mg silver bromide/dm and at about 30 mg gelatin/dm on cellulose triacetate film base. The coated films were subjected to both ESR and sensitometric measurements at room temperature. 

Fig. 22. FVactions of developed silver-bromide grains after deposition of size-selected silver clusters (Ag n = 2-4) as a function of the redox potential. Solid squares show the data in the cluster-exposed area open circles show those in the unexposed area (fog) as references. The silver dimer, panel (a), exhibited no influence in the catalysis of the reduction of the grains. On the other hand, the tetramer, panel (c), catalyzed the reaction in the redox potential range between —360 and —320 mV. (Adapted from Ref. 34.)...

A latent image is the result of a stepwise formation of nuclei that later may activate the reduction of the entire grain by the developing solution (a reducer). The photogenerated electron holes are rapidly trapped by the available vacancies. The photoelectrons, on the other hand, are not trapped by the silver interstitials in the interior of the silver bromide grain but only by the interstitials in suitable places on the surface. The activating silver metal nuclei are formed at the surface. 

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