Sensitization of non-screen type x-ray emulsions with aqueous solutions of ammonium or alkali aurous thiocyanates leads to a wave-length dependent increase of their x-ray and gamma-ray sensitivities. For a particular fine-grain emulsion the gain in photographic speed is shown to increase from a factor of 1.5 at 1.3A to a factor of 10 at 0.011A. This wave-length dependence of the sensitizing effect is governed by the range—energy relationship of electrons, by the shape of the energy loss curve of electrons, and the threshold sensitivity of the average grain. The sensitivity of the average grain in an unsensitized and a gold-sensitized emulsion was derived from the number of quanta required to produce the same photographic effects at different wave-lengths. Gold sensitization caused an increase in threshold sensitivity from (6 kev)−1 to (1.2 kev)−1 for the average grain of the emulsion under investigation. A comparison of the quantities of latent image silver formed by light exposure on one hand, and by electrons on the other, indicates that gold sensitization increases the effective radius of action of the sensitivity centers and also the number of active centers at the grain surface.
© 1950 Optical Society of AmericaFull Article | PDF Article
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