Spectra liquid phases

Vibrational transitions accompanying an electronic transition are referred to as vibronic transitions. These vibronic transitions, with their accompanying rotational or, strictly, rovibronic transitions, give rise to bands in the spectrum, and the set of bands associated with a single electronic transition is called an electronic band system. This terminology is usually adhered to in high-resolution electronic spectroscopy but, in low-resolution work, particularly in the liquid phase, vibrational structure may not be resolved and the whole band system is often referred to as an electronic band. 

Figure 9.18 shows a typical energy level diagram of a dye molecule including the lowest electronic states Sq, and S2 in the singlet manifold and and T2 in the triplet manifold. Associated with each of these states are vibrational and rotational sub-levels broadened to such an extent in the liquid that they form a continuum. As a result the absorption spectrum, such as that in Figure 9.17, is typical of a liquid phase spectrum showing almost no structure within the band system. 

If the same procedure is applied to real IR or FIR spectra then the deviation from the Lorentzian shape of the spectrum (2.74) may be found in the wings. These are expected to be pronounced in the liquid phase. 

Let us analyse the consequences of account being taken of the codependence of Xjj in the central part of the liquid phase P-R doublet in the IR spectrum of a linear rotator. For this purpose, we consider the... 

The liquid phase cage model accounts for appearance in the spectrum of resolved rotational components by effective isotropization of the rapidly fluctuating interaction. This interpretation of the gas-like spectral manifestations seems to be more adequate to the nature of the liquid phase, than the impact description or the hypothesis of over-barrier rotation. Whether it is possible to obtain in the liquid cage model triplet IR spectra of linear rotators with sufficiently intense Q-branch and gas-like smoothed P-R structure has not yet been investigated. This investigation requires numerical calculations for spectra at an arbitrary value of parameter Vtv. 

Above the eutectic temperature in the iron-FcsC system (1130°C)12, growth of large graphite plates and flakes occurs from the liquid phase. Carbon precipitates in the form of highly ordered graphite crystals from molten iron supersaturated with carbon. The Raman spectrum for chlorination at 1200°C is shown in Fig. 2c. A very strong and narrow... 

Certain features of light emission processes have been alluded to in Sect. 4.4.1. Fluorescence is light emission between states of the same multiplicity, whereas phosphorescence refers to emission between states of different multiplicities. The Franck-Condon principle governs the emission processes, as it does the absorption process. Vibrational overlap determines the relative intensities of different subbands. In the upper electronic state, one expects a quick relaxation and, therefore, a thermal population distribution, in the liquid phase and in gases at not too low a pressure. Because of the combination of the Franck-Condon principle and fast vibrational relaxation, the emission spectrum is always red-shifted. Therefore, oscillator strengths obtained from absorption are not too useful in determining the emission intensity. The theoretical radiative lifetime in terms of the Einstein coefficient, r = A-1, or (EA,)-1 if several lower states are involved,... 

Utilizing the same aryl fluoride linker on conventional MeOPEG polymer, these authors also presented a microwave-accelerated liquid-phase synthesis of benzimidazoles (Scheme 7.70) [79]. This bicydic pharmacophore is an important and valuable structural element in medicinal chemistry, showing a broad spectrum of pharmacological activities, such as antihistaminic, antiparasitic, and antiviral effects. 

Experiments at high pressure have shown that the P-T phase diagram of butadiene is comparatively simple. The crystal phase I is separated from the liquid phase by an orientationally disordered phase II stable in a narrow range of pressure and temperature. The strucmre of phase I is not known, but the analyses of the infrared and Raman spectra have suggested a monoclinic structure with two molecules per unit cell as the most likely [428]. At room temperature, butadiene is stable in the liquid phase at pressures up to 0.7 GPa. At this pressure a reaction starts as revealed by the growth of new infrared bands (see the upper panel of Fig. 25). After several days a product is recovered, and the infrared spectrum identifies it as 4-vinylcyclohexene. No traces of the other dimers can be detected, and only traces of a polymer are present. If we increase the pressure to 1 GPa, the dimerization rate increases but the amount of polymer... 

The subsurface liquid phase generally is an open system and its composition is a result of dynamic transformation of dissolved constituents in various chemical species over a range of reaction time scales. At any particular time the liquid phase is an electrolyte solution, potentially containing a broad spectrum of inorganic and organic ions and nonionized molecules. The presently accepted description of the energy characteristics of the liquid phase is based on the concept of matrix and osmotic potentials. The matrix potential is due to the attraction of water to the solid matrix, while the osmotic potential is due to the presence of solute in the subsurface water. 

The NH stretching band in triazole appears in the vapor phase at 3522 cm and in carbon tetrachloride at 3470 cm in the solid phase the NH absorption is a broad band at 2400-3300 cm (for 4-phenyl-triazole). The CH stretching frequency of 4- or 5-unsubstituted triazoles is at 3100-3140 cm (liquid phase).In-plane and out-of-plane deformation bands of the CH bond have also been distinguished at 1237 and 1076 cm (in the solution spectrum of 1,2,3-triazole), at 1290-1150 and 850-700 cm (for various substituted triazoles) and at 1149—1074 and 855-825 cm (for 2-aryltriazoles). ... 

Osmiumfvi).—The i.r. spectrum of [OsOCl ] has been recorded in the gas and liquid phases, and in solution. While the exact geometry could not be deduced, evidence was obtained for facile co-ordination of acetone or ether to the species in inert solvents. A mass spectral study of this complex reveals a complex fragmentation pattern, including the previously unknown [OsOClj] species. ... 

The IR spectra of 2,3 -bipyridine,i " - ° - i 2,4 -bipyridine, " 3,3 -bipyridine, °° and 3,4 -bipyridine °°- have all been reported. From IR spectral assignments it is suggested that 2,3 - and 3,3 -bipyridines adopt the cisoid conformation. The IR spectrum of 4,4 -bipyridine both in the solid state and in solution has attracted much attention, and the spectrum has been fully interpreted.4,4 -Bipyridine has been included in a study of the use of IR intensities as a quantitative measure of intramolecular interactions. Interestingly, changes in the intensities of IR bands due to aromatic ring deformations and C—H deformations on going from the solid to the molten state have been used to show that the aromatic rings of 2,2 - and 4,4 -bipyridines are not coplanar in the liquid phase. The IR spectra of salts of 4,4 -bipyridine have been discussed. ... 

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