Pressure electronic transitions

Drickamer H G and Frank C W 1973 Electronic Transitions and the High-Pressure Chemistry and Physics of Solids (London Chapman and Haii)... 

Present in the next sections are the LDA results for equilibrium structure, pressure-induced transitions and electronic properties of various polymorphs, and the comparative analysis of the results for rutile and anatase that were obtained using LDA and GGA forms of the exchange-correlation potential. 

Electronic transitions in transition metal compounds at high pressure. H. G. Drickamer, Angew. Chem., Int. Ed. Engl., 1974,13, 39-47 (34). 

Drickamer HG, Frank CW (1973) Electronic transitions and the high pressure chemistry and physics of solids. Chapman and Hall, London... 

Figure 33. Pressure dependence of the electronic transition energies of [Cu(dieten)2](BF4)2 polycrystalline (left panel) and in polyvinyl pyridine matrix (right panel).

Pressure provokes transition of the linear (extended) conformation into the bent (V-like) one. (The V-like form is more compact and occupies a smaller volume.) It is obvious that the V-like form is favorable in respect of intramolecular electron transfer from the donor (the aniline part) to the acceptor (the pyrene part). In the utmost level of the phenomenon, the donor part transforms into the cation-radical moiety, whereas the acceptor part passes into the anion-radical moiety. Such transformation is impossible in the case of the extended conformation because of the large distance between the donor and acceptor moieties. The spectral changes observed reflect this conformational transition at elevated pressures. 

Dr Irwin Wieder, Dr R.R. Neiman Dr A.P. Rodgers of Interphase Corporation-West, Palo Alto, Calif studied the IR and UV radiation emitted by excited species in low-pressure gaseous C2H2/O2 explosions in order to establish the population distribution in selected energy levels. In the UV they used cavity techniques, and found a relative enhancement of several electronic transitions in CH and OH radicals. In the IR the emission from excited CO2 molecules which form behind a fast detonation... 

G. C. Tabisz. Pressure dependence of the electronic transition <— 3Eg in the absoption spectrum of compressed oxygen. Chem. Phys. Lett., 9 581, 1971. 

A calculation of the oscillator strength of the y band was made by Erkovich.130 Using low-pressure absorption spectra, he obtained a value of0.043. This result is about 20 times as great as from other measurements, and the method used has been severely criticized by Penner.342 Erkovich and Pisarevskii,131 using a modification of Erkovich s method, calculated the electronic transition moments for the / and y systems. Because their computations were, as before, based on low-pressure absorption spectra, Penner s criticism still applies. 

The electronic transitions of silicalite and TS-1 in the UV-visible spectrum have provided significant information about the structure of TS-1. The diffuse reflectance spectra of the two materials (Fig. 11) show a strong transition at 48,000 cm-1 that is present in the spectrum of TS-1 and absent from that of silicalite. This transition must be associated with a charge-transfer process localized on Tiiv. The frequency of this transition is modified by the presence of H20 (Fig. 12). As the H20 partial pressure increases, the peak at 48,000 cm- is progressively eroded with formation of a lower-frequency absorption, which reaches a new stable maximum value at 42,000 cm. These frequencies come very close to those that can be calculated by the Jorgensen equation for Tiiv tetrahedrally and octahedrally coordinated to oxygen, respectively. Furthermore,... 

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