Silver chloride tabular grains with {100} faces on the surface (hereinafter referred as {100} tabular grain) were prepared by introducing a small amount of silver bromide at their nucleation stage. Their dislocation structure was observed by low-temperature transmission electron microscopy (LTEM) in order to study the mechanism of their anisotropic growth. The results of the observations were as follows: First, a nucleus was observed at one of the corners of almost every {100} tabular grain. Second, two dislocations extended from a nucleus trace in the <310> directions. Third, a {100} tabular grain grew anisotropically from the nucleus only in the two directions to which these two dislocations extended. Fourth, the dislocations thus observed in {100} tabular grains were identified as screw dislocations. We conclude that anisotropic growth of {100} tabular grains is caused by screw dislocations.

On the mechanism of nucleation and growth of (111) tabular silver halide crystals, it is proposed that twinning (nucleation) occurs by stacking fault and that the anisotropic lateral growth is brought about by the ridge trough structure on tabular grain side faces. Although the “coalescence” model for nucleation and the “rough-smooth” side face structure for anisotopic growth were proposed recently, they have not yet been supported by direct experimental evidence. We analyzed the nucleation process by a combination of light scattering and X-ray diffraction and examined the coalescence of untwinned fine grains after decomposition of gelatin. These experimental results provided evidence to support the coalescence model for twinnning. We observed by TEM imaging of ultramicrotomed sections of side faces of tabular grains that have relatively thick spacings between parallel twin planes and confirmed that on the side faces of tabular grains, both rough-smooth and ridge-trough structures exist.

The photographic sensitivity of a series of sulfur-plus-gold sensitized AgCl cubic emulsions ranging in size from 0.29 to 3.14-μm (cube edge length) was established in a model color-forming single-layer format. Each emulsion was spectrally sensitized to green light with a single sensitizing dye. The measured sensitivity gains with increasing grain size fell considerably short of those expected from simple surface area per grain considerations, thus confirming the limited potential of AgCl cubic grain technology in exposure-limited photographic applications. An additional shortcoming of using increased grain volume to obtain increased sensitivity was evident by the six-fold decrease in maximum density exhibited through the thousand-fold grain volume change. As part of this study, a highaspect-ratio {100} tabular grain AgCl emulsion (1.94 × 0.14 μm) was included for comparative purposes. This tabular grain emulsion, when sensitized in a fashion similar to that of the cubic emulsions, yielded a photographic response consistent with increased surface area per grain and more in line with the expected dye speed versus grain surface area relationship of the cubes.

In this series of investigations with a sulfur-sensitized cubic silver bromide emulsion with 9-methylthiacarbocyanine dye as a spectral sensitizer, we propose a new mechanism of dye desensitization according to which the enhancement of dispersion of image centers by cyanine dyes brings about a decrease in sensitivity. In the light of the fact that introduction of crystal defects into emulsion grains depressed the dispersion of image centers, a study was made of the dependence of the desensitization on the crystal defects introduced into the emulsion grains without causing any change in their size, shape, and halogen composition, effected by adding a solution of the dye during their growth process. The observation that the crystal defects actually depressed the desensitization strongly supports the proposed mechanism of dye desensitization.

Using a laser double ablation reactor built on the basis of a tandem time-of-flight mass spectrometer (TOF MS), we studied the reaction of clusters produced by laser ablation of silver (potassium) bromide and silver sulfur powder mixture. The results showed that reactions took place and that Ag/S/Br ternary cluster anions were produced. The formation of Ag/S/Br clusters is considered to occur by the addition of bromine atom to the silver sulfide cluster anions. The results provide grounds for the argument we proposed that silver sulfide cluster anions can act as positive hole traps during the exposure of photosensitive silver bromide microcrystals.

The influence of phase boundaries on the photoelectron lifetime of T-grain emulsion crystals is examined with the microwave absorption method. For the measurements, AgBr_1−xI_xT grains with a core-shell and a so-called “gradient” structure were used. The core-shell ratio, the grain volume, and the iodide content of the core were varied. The microwave absorption measurements indicated that a maximum photoelectron lifetime can be reached for a special combination of these parameters. In the case of core-shell T grains, maximum values were found for a core-shell ratio of 1:1 and iodide contents x > 0.08. For iodide values x < 0.02 “gradient” grains lead to the highest photoelectron lifetimes. A model is proposed to explain the behavior of the structured grains influenced by the interplay of the geometrical grain structure and the iodide content.

Experimental results on transient photoconductivity in AgBr emulsion grains as observed by a radiowave photoconductivity technique are reported. The decay component of the photoconductivity over several tens of microseconds observed using hole-injecting dyes is ascribed to photoholes in accord with the result reported by Kellogg, Hodes, and Muenter. We study dependence of the decay time of photoholes on grain size, excitation intensity, and pH and pAg of reaction solutions during AgBr precipitation. Hole traps in AgBr emulsion grains are ascribed to silver clusters in the grains. We discuss hole-trapping properties of some extrinsic centers detected by the technique.

The ultraviolet (UV) spectra and the pK_a and pK_sp of 14 different variations of 4-hydroxy-1,3,3a,7-tetraazaindene (TAI) measured in water at 25°C are discussed in this report. The acidity of the tautomeric proton correlated with the inductive electronic effect of the substituent as measured by Hammett' σ_ρ constants; pK_a values obtained potentiometrically and spectrophotometrically ranged from 3.4 to 6.5. The solubility products of the 1:1 TAI:Ag salts were measured at equilibrium using a solid-state silver sulfide electrode. The pK_sp values ranged from 9.6 to 12.9 and increased with substituent bulk at the 2 position and with electron-withdrawing substituents at the 5 position. Oxidation of an alkylthio substituent at either the 2 or 5 position decreased the pK_sp value. A carboxylic acid group at the 2 position yielded a soluble silver complex with log β₁ of 7.9; however, carboxylic acid substitution at the 5 position yielded a sparingly soluble salt with pK_sp of 10.4. Values of pK_a and pK_sp were observed to be correlated only for substituents in definite homologous series; however, there was no general correlation within the 14 examples.

The design of blue-light-sensitive layers in film systems can be limited by the relatively low extinction coefficients of chromogenically formed yellow imaging dyes. The release of a preformed dye from part of the coupling-off group of a coupler increases the effective extinction and is useful provided the dye is shifted to be colorless or nearly so, when part of the coupler. The overall hue of the dyes formed must be equivalent to the hue of the conventional dye system, and the incorporation of the dye into the coupling-off group cannot adversely affect the rate of reaction with oxidized color developer. In previous work on releasable dyes with phenolic chromophores, the dyes suffered from deficiencies that the hue was sensitive to pH, and often mordants were needed to prevent hue shifting. Such problems are overcome by using uncharged azo and methine chromophores. Release of the dye is made from carbamate precursors, which are, in turn, directly or indirectly linked to the coupling site of the coupler. The formation of the dye carbamate results in hypsochromic hue shifting of almost 100 nm.