X-ray exposures are supposed to result in the production of a considerable amount of internal latent image. However, in a motion-picture positive emulsion hardly any internal latent image could be developed after exposure to x-rays, at the temperature of liquid nitrogen as well as at room temperature. Since the existence of a marked Herschel effect shows that a considerable number of grains carry not more than one surface center, and that of minimum size, the question arises as to where the many hundred silver atoms have gone which were produced in the grain by the absorption of one x-ray quantum. They could have disappeared by rebromination in the absence of a halogen acceptor, or they could be too finely distributed to act as development centers. A reversal of the Herschel effect at high densities, after an x-ray exposure at the temperature of liquid nitrogen, argues for the second assumption.
G. KORNFELD, "Latent-Image Distribution by X-Ray Exposures," J. Opt. Soc. Am. 39, 1020-1021 (1949)