Resonance effects infrared

The infrared absorption frequencies of frans-3-substituted methyl acrylates gave a significant correlation with eq. (2). The value of p obtained is 75, which indicates predominance of the resonance effect. Three sets of nmr chemical shifts also were studied. All three sets gave significant correlation with eq. (2). The values of p obtained in two of the three sets were 70 and 78. Again, the resonance effect appears to predominate. 

The theoretical substituent resonance effect scale is based on ab initio calculations of electron populations in substituted ethylenes. A suitable regression equation is again established by using standard substituents, but now the quantum mechanical quantity is correlated with infrared-based <7,5 values. This equation is then the basis for theoretical Og° values of more than 40 substituents including SOMe and SOjMe at — 0.03 and 0.05 respectively. The latter agrees well with the infrared-based value of 0.06, and the former supports the occurrence of a — R effect as in the infrared value of — 0.07 cf. the value of 0.0 given by Ehrenson and coworkers . 

The sensitivity limitations of TLC-FT-Raman spectroscopy may be overcome by applying the SERS effect [782]. Unlike infrared, a major gain in Raman signal can be achieved by utilising surface activation and/or resonance effects. Surface-enhanced Raman (SER) spectra can be observed for compounds adsorbed on (rough) metahic surfaces, usually silver or gold colloids [783,784], while resonance Raman (RR) spectra... 

The frequency at which this resonance effect occurs (in Pat) is of the order of 1013 c/s, so dispersion occurs in the infrared region and an infrared absorption band can be observed. Only Pei remains above a frequency of 1014 c/s. 

Electron and hole effective masses of various SiC polytypes have been determined by various methods, such as Hall measurements, Faraday rotation, Zeeman splitting of a photoluminescence line, electron cyclotron resonance, and infrared light reflection. There have also been several theoretical studies of the effective masses of 3C-SiC. The effective masses of electrons and holes thus obtained are listed in TABLE 1. 

A theoretical scale of substituent resonance effects was based on calculations of electron populations in substituted ethylenes ". A suitable regression equation was again set up by using standard substituents, but in this case the quantum-mechanical quantity was correlated with infrared-based cr values. The equation was the basis of theoretical gr values for more than forty substituents. In this case it was possible to include the data for CN in the setting up of the regression equation, and the theoretical value for (t came out in exact agreement with the experimental value which had been used, namely 0.09. A... 

We have proposed a simple electromagnetic model of the CNT bundle, in which the bundle is considered as a system of coaxial thin-walled cylinders with effective conductivities. The bundle surface wave phase velocity was found increasing with the bundle radius. This shifts the frequency of geometric resonances into infrared range as compared with a single-wall CNT. 

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