Electronic band spectrum

It follows from eq. (3) that the thermopower must change linearly with the temperature. In most ternary stannides the dependence S T) is complex. Analysis carried out by Skolozdra (1993) shows that the deviations from linearity mainly correlate with the ones in the p(T) dependence and are caused by the same type of mechanisms of the electron scattering. The main causes of the anomalous 5(T) are the peculiarities of the structure of the electron band spectrum in the region of the Fermi level, a strong electron-phonon interaction, and the presence of a statistical distribution of atoms in the crystal structure. 

Figure 23.12 The Electronic Band Spectrum of Diatomic Nitrogen.

The most widely employed optical method for the study of chemical reaction dynamics has been laser-induced fluorescence. This detection scheme is schematically illustrated in the left-hand side of figure B2.3.8. A tunable laser is scanned tlnough an electronic band system of the molecule, while the fluorescence emission is detected. This maps out an action spectrum that can be used to detemiine the relative concentrations of the various vibration-rotation levels of the molecule. 

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. 

Ionization by electron impact has been shown (11) to occur at about 16.1 volts. Condon has given the explanation of the discrepancy between this and the band spectrum value in terms of... 

FIGURE 2.1 Energy of the 0-0 vibrational transition in the principal electronic absorption spectrum of violaxanthin (l Ag-—>1 BU+), recorded in different organic solvents, versus the polarizability term, dependent on the refraction index of the solvent (n). The dashed line corresponds to the position of the absorption band for violaxanthin embedded into the liposomes formed with DMPC (Gruszecki and Sielewiesiuk, 1990) and the arrow corresponds to the polarizability term of the hydrophobic core of the membrane (n = 1.44). 

The ultraviolet (UV) spectrum of compound 8 in dioxane showed two absorption bands at 463 and 350 nm. In the case of compound 6 (R = C6H5), the electronic absorption spectrum showed absorptions at 281 and 377 nm in dioxane... 

Figure 10.8 Room temperature electronic absorption spectrum recorded on a THF solution of 6. Bands are marked by the nominal Russell-Saunders multiplet to which the excitation occurs. (Adapted from Ref. [34], Copyright (2011) Nature Publishing Group.)...

The M(VI) oxidation state is represented in the 4d series by the hexafluorides, MFg, of the elements Mo, Tc, Ru, and Rh. All are obtained by direct fluorination of the metal and are unstable powerfully oxidising species — once again the instability seems most marked at the end of the series. Unfortunately hardly any electronic spectral data exist. The first charge-transfer band of the d°MoF(s has been located at 54 kK. (42), and a study of the vibrational spectrum of RuF6 (43) revealed electronic bands at 1.95 and 1.4 kK., which are probably the F2, r5 Ti, and /13,... 

As has been noted above, [Fe(HB(pz)3)2] undergoes a color change from deep violet to white upon heating, a change that is clearly revealed in its electronic absorption spectrum, see Fig. 4. The 297 K spectrum is dominated by a very intense charge-transfer band centered in the ultraviolet region and a less intense band centered at 19,000 cm-1. These absorptions account for... 

The electronic absorption spectrum of 190 exhibits a split Q band with peaks at 632 and 554 nm and the Soret band is found at 338 nm. Additionally, a peak is observed at 427 nm and assigned to O-pz, n-ji transition. The electrochemical properties of 189 and 190 have been studied by cyclic voltammetry in CH2C12. Compound 190 exhibits one reversible oxidation at Em = +0.73 V (vs Fc+/Fc) (11). 

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