Valence-optical theory

Gribov has provided an early detailed description of die valence optical theory in a well known book [72]. The derivation is based on expressing the dipole moment as... 

The bond charge parameter formulation developed by Van Straten and Smit [92] describes infi-ared intensities in terms of static bond charges and bond charge fluxes induced by vibrational distortions. In the mathematical procedure many common features with the )paratus of the valence-optical theory are present. 

B. Valence Optical Theory of Raman Intensities An Example... 

The valence-optical theory of Raman intensities (VOTR) is the first comprehensive theoretical formalism for interpreting vibrational intensities in the Raman... 

The indices 1, 2 and 3 correspond to the numbering of unit vectors as defined above. At diis stage important approximations are introduced. It is required diat the unit vector e Ik) lies always along the bond k and that the bond polarizability tensor preserves its simple representation when the bond participates in vibrational motion. These approximations are kept in order to reduce the number of intensity parameters. A generalized version of the valence-optical theory of Raman intensities which considers ofiT-diagonal elements of the bond polarizability tensor has been discussed by Rupprecht [299]. 

Cartesian reference fiame, geometrical data, definition of internal and symmetry coordinates and a matrix for sulfiir dioxide were already given in Section 9.I1.B. The application of valence-optical theory of Raman intensities results in the set of electro-optical parameters given by Eq. (9.43). If these quantities are substituted inside the brace of Eqs. (9.33) and (9.34), the elements of ([a]) array are obtained... 

The present book appears more than ten years since the publication of "Vibrational Intensities in Infrared and Raman Spectroscopy," a volume edited by W. B. Person and G. Zerbi. It contains comprehensive reviews describing major developments in the field made during the seventies. Though not at a very fast pace, advances in the field, especially in theoretical approaches, have been made during the past fifteen years. In 1988 the monograph of L. A. Gribov and W. J. Orville-Thomas "Theory and Methods of Calculation of Molecular Spectra" was published. This volume presents, in detail, the progress achieved within the valence optical theory of infrared and Raman intensities. 

The mean-square optical anisotropies of four oligomers of polyoxyethylene glycol dimethyl ether are determined from measurements of depolarized Rayleight scattering. They are interpreted using the valence optical scheme and RIS theory. 

The importance of the intensity datum has been re-discovered, when the schools of Gribov in Russia [8] and later of Gussoni in Milano [7,9-12] have presented and developed the "optical theory of valence". The important concept of such a theory lies in the fact, that the instantaneous M can be expressed as a sum of bond dipole moments directed at any instant along the bonds... 

L. M. Sverdlov, Theory of the Infrared Spectra Intensities of Polyatomic Molecules in the Zero and the First Approximation of a Generalized Valence-Optical Scheme, Optika i Spektroskopiya 10,152-156,1961. 

Noodleman, L., 8c Baerends, E. J. (1984). Electronic structure, magnetic properties, ESR, and optical spectra for 2-iron ferredoxin models by LCAO-Xa valence bond theory. Journal of the American Chemical Society, 106, 2316. 

Elliott C M, Derr D L, Matyushov D V and Newton M D 1998 Direct experimental comparison of the theories of thermal and optical electron-transfer studies of a mixed-valence dinuclear iron polypyridyl complex J. Am. Chem. 

A most important early addition to organic structure theory was made by the first Nobel Laureate in Chemistry, van t Hoff, who in 1874 recognized that the optical activity of carbon compounds can be explained by the postulate that the four valence bonds of the carbon atom are directed in space toward the comers of a tetrahedron. 

Azo-bridged ferrocene oligomers also show a marked dependence on the redox potentials and IT-band characteristics of the solvent, as is usual for class II mixed valence complexes 21,22). As for the conjugated ferrocene dimers, 2 and 241 the effects of solvents on the electron-exchange rates were analyzed on the basis of the Marcus-Hush theory, in which the t/max of the IT band depends on (l/Dop — 1 /Ds), where Dop and Ds are the solvent s optical and static dielectric constants, respectively (155-157). However, a detailed analysis of the solvent effect on z/max of the IT band of the azo-bridged ferrocene oligomers, 252,64+, and 642+, indicates that the i/max shift is dependent not only on the parameters in the Marcus-Hush theory but also on the nature of the solvent as donor or acceptor (92). 

In order to explain the changing optical properties of AIROFs several models were proposed. The UPS investigations of the valence band of the emersed film support band theory models by Gottesfeld [94] and by Mozota and Conway [79, 88]. The assumption of nonstoichiometry and electron hopping in the model proposed by Burke et al. [87] is not necessary. Recent electroreflectance measurements on anodic iridium oxide films performed by Gutierrez et al. [95] showed a shift of optical absorption bands to lower photon energies with increasing anodic electrode potentials, which is probably due to a shift of the Fermi level with respect to the t2g band [67]. 

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