Metastable state anionic

OXYGEN, OXIDES 0X0 ANIONS META-MODEL METAPHOSPHATE ACYL PHOSPHATES OXYGEN, OXIDES 0X0 ANIONS METASTABLE STATE JABLONSKI DIAGRAM TRANSIENT CHEMICAL SPECIES Metastable triplet state,... 

D.J. Haxton, C.W. McCurdy, T.N. Rescigno, Dissociative electron attachment to the H2O molecule I. Complex-valued potential-energy surfaces for the 2I1, 2A, and 2B2 metastable states of the water anion, Phys. Rev. A 75 (2007) 012710/1. 

If n denotes a resonant (metastable state) of the anion, E +1(t ) = Ej,+1 — ir/2 and the corresponding pole (Ejf+1( )—Eq ) = (Ej,+1— Eq )—iT/2 and from the real part one may directly determine the kinetic energy of the incident electron for which resonance occurs and the imaginary part provides the half width. These poles are persistent once uncovered. 

Cyanide. In contrast to [Fe(CN)6]4 , the [Fe(CN)6]3 ion is quite poisonous for kinetic reasons the latter dissociates and reacts rapidly, whereas the former is not labile. There is a variety of substituted ions [Fe(CN)3X]" (X= H20, N02, etc.), of which the best known is the nitroprusside ion [Fe(CN)5NO]2. Crystalline sodium nitroprusside dihydrate exhibits extremely long-lived electronic excited states.47 A metastable state I and a metastable state II have lifetimes greater than 104 s at temperatures below 185 and 140 K, respectively. The nitroprusside anion is attacked by OH to give [Fe(CN)5N02]2-. 

Stable and metastable states have been characterized for several negatively charged atoms and molecules both in their ground and/or electronically excited states. Long-lived electronically excited molecular systems, where the anionic electronic ground state is not bound, do exist and have been characterized experimentally. A detailed discussion and a full presentation of the examples known are reviewed in Refs. [5,6]. In this section, we are treating the case of the CS- anion. 

Ni and CNO can exist in a metastable state in ionic lattices. Among the azides, the anion is essentially unperturbed in the alkali metal salts but in the more complex heavy metal salts increasing perturbation of the anion occurs which is reflected in the asymmetric intraionic distances of the divalent salts in particular. This may be one of the reasons why the heavy metal salts are unstable with respect to the alkali metal azides. It is therefore pertinent to note that among the divalent azides the thermal sensitivity increases with the increasing asymmetry of the azide ions which increases in the order BaNe < PbNe < CuNe (c/. Table 2). Electron microscopic observations on thallous azide crystals have shown that the cubic form of the salt is relatively stable compared with the low temperature orthorhombic form (85). This is probably associated with the existence of asymmetric azide ions in the latter poljmiorph (c/.) Section IID). 

The relevance of the above kind of electronic shape resonance to chemistry Is twofold. First, In environments such as plasmas, electrochemical cells, and the ionosphere, where free electrons are prevalent, the formation of such temporary anions can provide avenues for the free electrons to "cool down by transferring kinetic energy to the Internal (vibrational and/or electronic) degrees of freedom of the fragment. (6-14) Second, metastable states may play Important roles in quenching excited electronic... 

Thermal shock produces an essential number of OFF defects in the oxygen sublattice. The concentration of defects grows rapidly during first picoseconds of simulation and than tends to stabilize. In the metastable state obtained about 40% of interstitial sites are populated by displaced anions (see Fig. 1). Kinetics of evolution of defects may be effectively studied by an instant dropping of temperature (quenching) of overheated solid up to temperature about 1000 K. At this temperature another short MD run (about -3-5 ps) was performed to study the relaxation of defect concentration. As it follows from Fig. 2, the defect concentration decreases almost exponentially with a relaxation time of - 2 ps. 

The rJ of the free acid decreases linearly with a small positive slope as the Z values rise. In contrast, the rJ of the uncomplexed anion, the species participating In complexatlon, drops sharply between Z values of 80 and 83, varying little above and below these values. Thus, the conformation of the anion tends toward one of two metastable states depending upon solvent Z value. 

When subjected to pressure, the coordination number of the cations, and anions, increases. In the case of silica, this has been an area of some conjecture. Some thirty years ago, a new phase of Si02 was discovered, i.e., stishovite. Stishovite can be formed from silica under pressure, yet it can exist in a metastable state under ambient conditions. In this form of crystalline silica,silicon is six-fold coordinated. Questions as to the denser forms of silica beyond stishovite have been raised in the context of mineral physics. 

IR spectroelectrochemical studies on Ru2(Fap)4(NO)Cl, where Fap = 2-(2-fluoroanilino)-pyridinate anion, show that NO remains bound in the complex on reduction and that the first reduction adds an electron to the Ru2 core and not to NO. There is IR evidence for Ru-NO/Ru-ON linkage isomerism in the metastable state I of frans-[Ru(NH3)4(NO)(nicotinamide)] +. ... 

As compared to the MOM approach discussed earlier, other methods for treating metastable states are somewhat more involved, and understanding them requires a few concepts that go beyond bound-state quantum mechanics. One idea that is needed is the notion of analytic continuation of the bound-state energy levels into the complex plane. A heuristic explanation of why this is necessary goes as follows.In some ways, a temporary anion resonance resembles a stationary state of the molecular potential, at least in the sense that the probability distribution is relatively localized around the molecule (see Figure 13). At the same time, however, the resonance has a finite lifetime and will ultimately tunnel out of the potential that is responsible for it. In view of these facts, it... 

There are other soUd states which sometimes confuse the measurement and definition of solubiUty. The dmg may crystaUize as a hydrate, i.e. under inclusion of water molecules. If the hydrate form is more stable than the pure form it may be difficult to measure the intrinsic solubility of the drug at all. Often drugs tend to precipitate in an amorphous form, often under the inclusion of impurities. As with metastable polymorphs, such amorphous precipitates may lead to erroneously high solubility measurements. CommerciaUy, drugs are often crystallized in salt form, e.g. as the hydrochloride salt, a cation with a chloride anion. In these co-crystallized salts, a much lower solubility than the intrinsic solubility will typi-... 

It was proposed that the increase in activity during the equilibration period was due to the generation of new active sites,consisting of the Mo species located in the cationic position in the secondary framework of the POM. A similar hypothesis was formulated by other authors for the methacrolein oxidation to methacrylic acid." " More generally, it is currently believed that for exothermic reactions, and specifically for oxidations, the true working state of the POM, does not correspond to its crystalline form." The presence of steam and the large amount of heat released provoke an incipient surface decomposition, which leads to the expulsion of the Mo species from the anion as a metastable defective... 

Particular care has been devoted to establishing a qualitatively correct description of the metastable anion state that arises. 

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