Anisotropy pair polarizability

Gelbart (1974) has reviewed a number of theories of the origins of the depolarized spectrum. One of the simplest models is the isolated binary collision (IBC) model of McTague and Bimbaum (1968). All effects due to the interaction of three or more particles are ignored, and the scattering is due only to diatomic collision processes. In the case that the interacting particles A and B are atoms or highly symmetrical molecules then there are only two unique components of the pair polarizability tensor, and attention focuses on the anisotropy and the incremental mean pair polarizability... 

A problem with studies on inert gas is that the interactions are so weak. Alkali halides are important commercial compounds because of their role in extractive metallurgy. A deal of effort has gone into corresponding calculations on alkali halides such as LiCl, with a view to understanding the structure and properties of ionic melts. Experience suggests that calculations at the Hartree-Fock level of theory are adequate, provided that a reasonable basis set is chosen. Figure 17.7 shows the variation of the anisotropy and incremental mean pair polarizability as a function of distance. 

Figure 17.7 Anisotropy (doited) and mean incremental pair polarizability...

Measurements. The anisotropy of the pair polarizability has been determined from three types of measurements depolarized CILS spectra, pressure dependent depolarization ratios, and second virial Kerr coefficients. 

F. Barocchi, M. Zoppi, U. Bafile, and R. Magli. The pair polarizability anisotropies of Kr and Xe from depolarized interaction induced light scattering spectra. Chem. Phys. Lett., 97 135-138 (1983). 

A. D, Buckingham and K. L. Clarke-Hunt. The pair polarizability anisotropy of SF in the point-atom-polarizability approximation. Molec. Phys., 40 643-648 (1980). 

P. R. Hilton and D. W. Oxtoby. Charge transfer in atomic collisions The pair polarizability anisotropy. J. Chem. Phys., 72 4Ti-4n (1980). 

N. Meinander, G. C. Tabisz, and M. Zoppi. Moment analysis in depolarized light scattering Determination of a single-parameter empirical pair polarizability anisotropy for Ne, Ar, Kr, Xe and CH. J. Chem. Phys., 54 3005-3013 (1986). 

N. Meinander, A. R. Penner, U. Bafile, F. Barocchi, M. Zoppi, D. P. Shelton, and G. C. Tabisz. The spectral profile of the collision induced translational light scattering by gaseous CH4 Determination of the pair polarizability anisotropy. Molec. Phys., 54 493-503 (1985). 

N. Meinander and G. C. Tabisz. Moment analysis and line shape calculations in depolarized induced light scattering Modeling empirical pair polarizability anisotropy. J. Quant. Spectres. Rad. Transfer, 55 39-52 (1986). 

Harder E, Anisimov VM, Vorobyov IV, Lopes PEM, Noskov SY, MacKerell AD, Roux B (2006) Atomic level anisotropy in the electrostatic modeling of lone pairs for a polarizable force field based on the classical Drude oscillator. J Chem Theory Comput 2(6) 1587-1597... 

Several types of collision-induced light scattering spectra are known. We have already mentioned the depolarized translational spectra of rare gas pairs and bigger complexes which arise from the anisotropy of the diatom polarizability. Contrary to the infrared inactivity of like pairs, e.g., Ar-Ar like pairs are Raman active. Furthermore, polarized translational spectra... 

The elements of o(co) are determined from studies of molecular refraction, anisotropic li t scattering, the Kerr effect, and optical birefiringence. Frequency-dependent polarizabilities can also be calculated directly to various orders of approximation by methods of quantum mechanics. Research has of late been developing on the spectra of depolarized li t in simple gases and liquids, " leading to the detemunation of pair polarizabOity of atoms or molecules - as wdl as of the polarizability anisotropies induced by multiple correlations. ... 

In general, the polarizability is a tensor whose invariants, trace and anisotropy, give rise to polarized and fully depolarized light scattering, respectively. Collision-induced light scattering is caused by the excess polarizability of a collisional pair (or a larger complex of atoms or molecules) that arises from the intermolecular interactions. In Section I.l, we are concerned with the definition, measurement, and computation of interaction-induced polarizabilities and their invariants. 

Induced polarizabilities differ from zero for a variety of reasons. A most important influence is the deviation of the local electric field from the externally applied laser field if another polarized atom or molecule is in close proximity. The classical dipole-induced dipole (DID) model considers the interacting pair as point dipoles [135, 136] and leads to separation-dependent invariants of the incremental polarizabilities [51, 62, 87, 115]. For the more highly polarizable particles, the DID anisotropy model is fairly accurate. Even for the less polarizable atoms such as helium and neon, at most separations of interest, the DID component of the anisotropy is known to be... 

L. Frommhold and M. H. Proffitt. About the anisotropy of the polarizability of a pair of argon atoms. Molec. Phys., 35 681-689 (1978). 

M. H. Proffitt and L. Frommhold. Concerning the anisotropy of the polarizability of pairs of methane molecules. Chem. Phys., 36 197-200 (1979). 

Figure 12 shows polymer concentration cP dependence of the anisotropy of the electrical polarizability Aa of a 64/128 base-pair DNA fragment. Aa increases on dilution of polymer concentration. Experimentally, Aa is determined via measurement of the Kerr constant of the polyelectrolyte solutions, and in the case of rodlike polyelectrolytes both quantities are proportional to each other. It has been observed that the Kerr constant of polyelectrolytes in salt-free aqueous solutions increases on dilution [46,47], This behavior of the Kerr constant is one of the characteristic properties of polyelectrolytes in salt-free aqueous solutions whose reproduction we have succeeded in by computer simulation. The figure also indicates that Aa is... 

FIG. 11 Partial anisotropies of the electrical polarizability Aa(n) determined for a 64 base-pair DNA at various polymer concentrations plotted against the number of... 

FIG. 12 Polymer concentration cP dependence of the anisotropy of the electrical polarizability Aa of a 64/128 base-pair DNA fragment. 

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