感光颗粒内碘离子的分布与乳化方法的关系

本文利用X射线光电子能谱法和X射线衍射分析,研究了双注法高感乳剂乳化过程中,碘离子的引入时刻对于乳剂颗粒内碘离子分布情况的影响.结果表明,一般说来,碘离子引入得愈早,则其出现在颗粒表面的可能性愈小;引入得愈晚,其位置愈靠近颗粒的表面.但是,早期引入碘离子同时,还有另一种效应,即倾向于使碘离子在体系中均匀分布,从而使其出现在颗粒表面的概率增大.有若干事实说明,这种“均化”效果可能是早期形成的碘化银或碘溴化银晶体在乳化过程中进行重结晶而引起的.在所有情况下,颗粒表面上均发现一层极薄的富碘层,其原因之一可能是碘离子在颗粒表面的富集可减少碘溴化银晶格的畸变.

IODIDE DISTRIBUTION IN PHOTOGRAPHIC GRAINS IN RELATION TO METHOD OF GRAIN PRECIPITATION

The iodide distribution in the silver iodobromide grains of a high-speed ammonia-cal emulsion is investigated in relation to the instant of time of iodide uncorporation into the emulsion during double-jet precipitation.The X-ray photoelectron spectro-scopic study confirms the general concept that the earlier the iodide incorporation, the less the possibility for the ions to come out to grain surface, and vice versa.However.as shown by X-ray diffraction analysis, with the shift of the instant of iodide incorporation from the end of the precipitation toward the beginning of the process, there occurs an increasingly narrowing of the diffraction profile of the grains, which implies an increasingly more uniform distribution of the iodide, ions through the grains.This "homogenization effect" in the grains, associated with an early iodide incorporation, is believed to be a consequence of a relatively long recrys’tallization and, hence, redistribution process of the silver iodide or silver iodobromide grains formed at the early stages of precipitation.The iodide-containing grains formed by the end of the precipitation are offered less chance of recrystallization and, therefore, a more uneven distribution of the iodide ions in the grains results.In all cases, the surface layer of the grains shows an iodide content considerably higher than might be expected based on a uniform distribution.One of the reasons for the surface enrichment with iodide ions could be the tendency of the grains for a reduction of the lattice distorsion which would arise to a greater extent with more iodide ions incorporated in the grain bulk.