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Type: Artigo de periódico
Title: Dynamic Atomic Contributions To Infrared Intensities Of Fundamental Bands
Author: Silva
Arnaldo F.; Richter
Wagner E.; Bassi
Adalberto B. M. S.; Bruns
Roy E.
Abstract: Dynamic atomic intensity contributions to fundamental infrared intensities are defined as the scalar products of dipole moment derivative vectors for atomic displacements and the total dipole derivative vector of the normal mode. Intensities of functional group vibrations of the fluorochloromethanes can be estimated within 6.5 km mol(-1) by displacing only the functional group atoms rather than all the atoms in the molecules. The asymmetric CF2 stretching intensity, calculated to be 126.5 km mol-higher than the symmetric one, is accounted for by an 81.7 km mol(-1) difference owing to the carbon atom displacement and 40.6 km mol(-1) for both fluorine displacements. Within the Quantum Theory of Atoms in Molecules (QTAIM) model differences in atomic polarizations are found to be the most important for explaining the difference in these carbon dynamic intensity contributions. Carbon atom displacements almost completely account for the differences in the symmetric and asymmetric CCl2 stretching intensities of dichloromethane, 103.9 of the total calculated value of 105.2 km mol(-1). Contrary to that found for the CF2 vibrations intramolecular charge transfer provoked by the carbon atom displacement almost exclusively explains this difference. The very similar intensity values of the symmetric and asymmetric CH2 stretching intensities in CH2F2 arise from nearly equal carbon and hydrogen atom contributions for these vibrations. All atomic contributions to the intensities for these vibrations in CH2Cl2 are very small. Sums of dynamic contributions of the individual intensities for all vibrational modes of the molecule are shown to be equal to mass weighted atomic effective charges that can be determined from atomic polar tensors evaluated from experimental infrared intensities and frequencies. Dynamic contributions for individual intensities can also be determined solely from experimental data.
Subject: Dipole-moment Derivatives
Polar Tensors
Vibrational Intensities
Absorption Intensities
Flux Interpretation
Red Intensities
Citation: Dynamic Atomic Contributions To Infrared Intensities Of Fundamental Bands. Royal Soc Chemistry, v. 17, p. 30378-30388 2015.
Rights: aberto
Identifier DOI: 10.1039/c5cp04949k
Date Issue: 2015
Appears in Collections:Unicamp - Artigos e Outros Documentos

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