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Distorted optical constant

In all the studies mentioned, the optical effect caused by the accumulated products of any electrode reactions (formally, by the appearance of an ultrathin film at the interface) was ignored. This effect produces the baseline distortions in the regions of the absorption bands of the solvent (Fig. 3.27). Using the air-water interface as an example, Buffeteau et al. [247] demonstrated that to reproduce these distortions correctly, the optical constants of interfacial rather than bulk water should be used in the spectrum simulations. As underlined by Chazalviel et al. [146, 147] for ATR spectra of a film at the semiconductor-water interface, the uncompensated absorption of the solvent due to increasing the film thickness can be either negative or positive. If the film is compact and has a low refractive index (this is... [Pg.210]

From more recent optical data it is proved that Qn(TCNQ)2 is a semiconductor up to 300 K, with an energy gap due mainly to a Peierls distortion on the conducting TCNQ chains [57]. However, this gap Ec = 2A is not constant, as is simply assumed in the model of Epstein et al. In fact, A appears to decrease significantly from = 1200 K at T = 0 K to = 300 K at T = 300 K, somewhat like in the salt TEA(TCNQ)2 (see above). This requires a modified approach in which the existence of a conductivity maximum cjm still implies a T-dependent mobility p, but not so steep as would require a constant gap. [Pg.336]

From the frequency of the transverse optical mode in a simple AB lattice with k = Q a force constant can be derived which is a measure of the restoring forces experienced by the atoms as they are distorted from the equilibrium position. This force constant, Fflattice), is a linear combination of internal force constants, since in a lattice a linear combination of equilibrium distances and angles yields a coordinate of this vibration. Based on this assumption, the GF method (Wilson et al, 1955) can be applied. For diamond (or zinc blende), the following relation is obtained ... [Pg.248]

The entrance optics to the analyser is usually chosen so that it can be tuned to nearly constant transmission over a large energy range. The gun optics is also usually chosen so that the beam can be focussed at the same position with the same image size over a wide energy range. This is necessary in order to avoid distortion of peak shapes and resonance features and inaccuracies in the cross-section measurements. After transmission through the analyser a simple lens transfers the electrons to the surface of an electron multiplier, usually a channeltron, which is operated in the pulse count mode. [Pg.16]


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