Silver atoms state

Techniques other than UV-visible spectroscopy have been used in matrix-isolation studies of Ag see, for example, some early ESR studies by Kasai and McLeod 56). The fluorescence spectra of Ag atoms isolated in noble-gas matrices have been recorded (76,147), and found to show large Stokes shifts when optically excited via a Si j — atomic transition which is threefold split in the matrix by spin-orbit and vibronic interactions. The large Stokes shifts may be explained in terms of an excited state silver atom-matrix cage complex in this... 

One way that a solid metal can accommodate another is by substitution. For example, sterling silver is a solid solution containing 92.5% silver and 7.5% copper. Copper and silver occupy the same column of the periodic table, so they share many properties, but copper atoms (radius of 128 pm) are smaller than silver atoms (radius of 144 pm). Consequently, copper atoms can readily replace silver atoms in the solid crystalline state, as shown schematically in Figure 12-4. 

A study518 of the mechanism of oxidation of alcohols by the reagent suggested that a reversible, oriented adsorption of the alcohol onto the surface of the oxidant occurs, with the oxygen atom of the alcohol forming a coordinate bond to a silver ion, followed by a concerted, irreversible, homolytic shift of electrons to generate silver atoms, carbon dioxide, water, and the carbonyl compound. The reactivity of a polyhydroxy compound may not, it appears, be deduced from the relative reactivity of its component functions, as the geometry of the adsorbed state, itself affected by solvent polarity, exerts an important influence on the selectivity observed.519... 

This linear combination is clearly different from (3). The implication is that the two-dimensional vector space needed to describe the spin states of silver atoms must be a complex vector space an arbitrary vector in this space is written as a linear combination of the base vectors sf with, in general complex coefficients. This is the first example of the fundamental property of quantum-mechanical states to be represented only in an abstract complex vector space [55]. 

In many instances, the above reaction will then take place in the reverse direction, and the silver atom will revert to the normal stable state as a Frenkel... 

Fig. 3-4. Energy for formation of gaseous silver ions in the standard state from siirface silver atoms of solid silver metal = unitary...

It was also observed, in 1973, that the fast reduction of Cu ions by solvated electrons in liquid ammonia did not yield the metal and that, instead, molecular hydrogen was evolved [11]. These results were explained by assigning to the quasi-atomic state of the nascent metal, specific thermodynamical properties distinct from those of the bulk metal, which is stable under the same conditions. This concept implied that, as soon as formed, atoms and small clusters of a metal, even a noble metal, may exhibit much stronger reducing properties than the bulk metal, and may be spontaneously corroded by the solvent with simultaneous hydrogen evolution. It also implied that for a given metal the thermodynamics depended on the particle nuclearity (number of atoms reduced per particle), and it therefore provided a rationalized interpretation of other previous data [7,9,10]. Furthermore, experiments on the photoionization of silver atoms in solution demonstrated that their ionization potential was much lower than that of the bulk metal [12]. Moreover, it was shown that the redox potential of isolated silver atoms in water must... 

CuO, the mineral tenorite, and AgO are well known but their structures are quite different. More importantly the valence states in these two compounds are quite different. In CuO, the copper is formally in the divalent state, whereas in AgO, there exist two types of silver atoms, one in formal oxidation state 1+, the other in 3+. These two silver ions also possess strong covalent character. PdO and CuO, however, have similar crystal structures based on chains of opposite edged-shared, square-planar M04 groups. 

For example, the -factor for the normal state of the neutral silver atom, assigned the symbol 4dlbL68 2/S f is observed to be 1.998, and the 0-factors for the first two excited states, 4d105p 2p and 2pf, are observed to be 0.666 and 1.330, respectively the theoretical values for these three states are 2.000, 0.667, and 1.333, so that the agreement is excellent, and one may conclude that the states are correotly assigned. 

The crystal structure of [Ag(en)]C104 has been determined.47 In solution, it has been suggested that the 1 1 complex may exist as a hydrated chelate with some strain within the five-membered chelate ring. In the solid state, however, the complex formed infinite chains (1) with a bridging ethylenediamine between the silver atoms.47... 

The crystal structure of [Ag P(0Me)3 2N03]2 has been determined.195 In the crystalline state, the structure consisted of a centrosymmetric dimer (21) containing a bridged nitrate. The bridging occurred via only one oxygen and this was equidistant from both silver atoms (Ag—O distances were 245.6 and 245.4 pm). The Ag—Ag separation was 409.5 pm, while the Ag—P bond lengths were 241.1 and 241.2 pm. 

Silver(I) oxide, [CAS 20667-12-3]. AgjO. is made by action of oxygen under pressure on silver at 300°C, or by precipitation of a silver salt with carbonate-free alkali metal hydroxide it is covalent, each silver atom (in solid AgjO) having two collinear bonds and each oxygen atom four tetrahedral ones two such interpenetrating lattices constitute the structure. Silver(I) oxide is die normal oxide of silver. Silver(II) oxide, AgO, is formed when ozone reacts with silver, and thus was once considered to be a peroxide, Silvcr(III) oxide, Ag203, has been obtained in impure state by anodic oxidation of silver. 

In an unsensitized grain, shallow trap states provided by crystal imperfections are important in the trapping of both electrons and holes. Hamilton assumes that the fraction of holes trapped is approximately 1, that is, the concentration of mobile holes is near 0. Nucleation to form silver is inefficient, and a high level of free-electron/trapped-hole recombination occurs. There is a certain probability, however, that a trapped electron will unite with a silver ion to form an atom which may either dissociate back into electron and silver ion or trap another electron and, with a second Ag, form a silver atom pair. This pair is relatively stable and can grow by... 

Some excited dye molecules can inject holes into the valence band of the silver halide. Photohole injection has been demonstrated experimentally by the photobleaching of chemically produced fog silver (248) to produce direct positive photographs. This action depends on the favorable location of the SQ ground state of the dye relative to the valence band of the silver halide. The injection is accomplished by the transfer of an electron from the valence band to the vacant SQ level of the excited dye molecule, leaving a mobile hole in the valence band which can oxidize a silver atom. Conversely, if the SQ level of a dye molecule is located sufficiently above the top of the valence band, a mobile hole in the silver halide can become trapped by the nonexcited dye. Hole-trapping by dyes has been detected by ESR signals (249,250). 

Demonstration 4.1 shows that the formation rate makes the difference. Glass, as it cools, solidifies quickly from the molten state. There is no time for the atoms and ions to line up in an orderly structure. They are frozen in place like pebbles in ice. Silver crystals, however, form slowly as silver atoms line up in a face-centered cubic arrangement. The atoms are as uniform as soldiers waiting for inspection. 

The dyes must also have appropriate redox properties to function properly as sensitizers. If the dyes are oxidized too readily in the ground state, silver atoms can be prematurely and unselectively reduced, and this causes photographic fog. Fog is the unwanted, indiscriminate reduction of silver. Photographic fog causes a loss of signal-to-noise ratio and degrades image quality. The redox potentials of sensitizing dyes have also been extensively measured and correlated to performance [15],... 

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