Photographic effects

It is clear that, along with the discovery of x-rays in 1895, Roentgen also found the chemical action of ionizing radiation. He drew attention to the similarity of the photographic effect induced by light and x-rays. Application to medicine appeared very quickly, followed by industrial applications. However, this field of investigation remained nameless until Milton Burton, in 1942, christened it radiation chemistry to separate it from radiochemistry which is the study of radioactive nuclei. Historical and classical work in radiation chemistry has been reviewed by Mozumder elsewhere [1]. Here we will only make a few brief remarks. 

BECQUEREL EFFECT, A photographic effect discovered by E, Becquerel (1895). Experimenting with the daguerreotype process. Becquerel found that a plate will produce a direct (positive) image if exposed first to diffuse daylight. See also Photochemistry and Photolysis and Photography and Imagery. 

The electron, if not lost by recombination or some secondary process, can combine with an interstitial silver ion or possibly a surface silver ion to form a silver atom. The photolytic silver is formed as, or aggregates to form, nuclei rather than existing as individual atoms distributed throughout the crystal. Only one nucleus consisting of a few silver atoms is needed to produce a detectable photographic effect. 

A photon absorbed by the adsorbed dye may have as much photographic effect as one absorbed by the silver halide, but not more. Usually less. The efficiency of spectral sensitization relative to the sensitivity for light absorbed by the silver halide in the presence of the dye is expressed as the relative quantum efficiency,... 

In the examples just given, the observed intensity was estimated simply by visual comparison of one line with another. Although this simple procedure is satisfactory in a surprisingly large number of cases, there are problems in which a more precise measurement of diffracted intensity is necessary. Two methods are available for making such measurements, one dependent on the photographic effect of x-rays and the other on the ability of x-rays to activate an electronic counter. These methods have already been mentioned briefly in Sec. 1-8 and will be described more fully in Chaps. 6 and 7, respectively. 

Light-induced Electron Spin Resonance Signals of Dyes on the Surface of Silver Bromide Microcrystals Photographic Effects... 

To illustrate ligand and lattice effects more clearly, a reasonably comprehensive set of kinetic data for a range of transition-metal complexes in the silver halides is presented in Table 11. It is clear from the results included for Ir3 + and Rh3 + that aquation leads to a significant increase in the lifetime of the trapped electron state. This must cause important changes in the photographic effects associated with the addition of a particular impurity ion. In the case of Ir3+, such differences in lifetime do not appear to result from a... 

If exposures of several weeks are needed, the thin-layer chromatogram and film are kept in a refrigerator to prevent secondary photographic effects. 

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

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