Kerr-Constant Measurements

Dipole moments and molar Kerr constants of phenotellurazines were measured (85ZOB846). The results suggest a significant shift of electron density from the benzene rings toward the heterocycle. 

Measurements of dipole moments, Kerr constants, and dielectric absorption have been employed (81RCR336) widely to obtain information on the conformational equilibrium in acyl heterocycles. Details on conformer structures and populations depend on the choice of additive scheme, group moments, or polarizability tensor in the case of Kerr constants. Several early conclusions, especially for furan- and thiophene-2-carboxaldehyde, appeared contradictory, owing to the choice of these quantities. A more precise definition of polarizability tensors for several heterocycles and a choice of group moments and additive schemes tested on a large amount of available experimental results and supported by accurate theoretical calculations have led to more confidence in the use of experimental dipole moments and Kerr constants in conformational analysis. A limitation of the method is that the... 

Dipole moments and Kerr constants of dibenzoates of several diols are measured at 298 K. Theoretical analysis is performed with standard methods of the RIS model. Comparison of theory with experiment indicates that is almost insensitive to the conformational energies, particularly for m > 3. Kerr constants are much more sensitive to the conformational energies. Good agreement between theoretical and experimental values of both dipole moments and Kerr constants of all these compounds is achieved by adjustement of the optical parameters and the... 

The dipole moment of 1,10-phenanthroline was first measured by Fielding and Le Fevre,18 who obtained a moment of 4.1 D, close to the value of 3.8 D expected for the hypothetical m-2,2 -bipyridyl. Since then the dipole moments of the phenanthrolines have been studied by other groups.16,17,64 The experimental values are recorded in Table I. They were found to be in good agreement with values computed by the vector addition of the moments of the individual pyridine nuclei. The molecular polarizability of 1,10-phenanthroline has been further studied and its molar Kerr constant determined.65... 

SLS, birefringence, dielectric constant Kerr effect) measurements... 

It is costumary to refer to as the experimentally measured Kerr constant , in spite of the fact that 5a is in general not constant but depends on the wavelength A of the analysing light, the structure and thermodynamic state of the medium, and (as is the case in macromolecular substances) the applied field strength. -In conformity with (160), the molar refraction too is a fimction of the static field ... 

Hence, once the correlation parameter /g of the pure solvent is available, equation (228) permits the determination of the parameter of cross-angular correlations A . Recently, Stiles determined the value of A for several dipolar liquids by measuring the Kerr constant in dilute solutions in benzene. However, the A values thus obtained, e.g. for the benzene-nitrobenzene correlation, J ii, differ in sign from the value... 

In general, the change in volume caused by the field E consists of an isotropic contribution AF and an anisotropic one AF f ". The latter is chiefly due to shape deformation of the dielectric sample. In fact, it should be stated that an isotropic body can exhibit anisotropic electrostriction, accorfhng to the method adopted by the experimenter this eventuality should be eliminated as far as possible in measurements. The constant given by (164b) is non-zero only if the electrostriction apparent in the macroscopic medium is anisotropic. Anisotropy of electrostriction can to some degree affect the measurement of the Kerr constant but if the necessary precautions are taken, the part due to is eliminated completely or at least made quite insignificant. 

In the expressions (184) and (184b) the second, temperature-dependent term defines the Born effect due to superposition of the two non-linear processes of second-order distortion and reorientation of permanent dipole moments in the electric field. Buckingham et al. determined nonlinear polarizabflities If and c for numerous molecules by Kerr effect measurements in gases as a function of temperature and pressure. It is here convenient to use the virial expansion of the molar Kerr constant, when the first and second virial coefficients Ak and Bk result immediately from equations (177), (178), and (184). Meeten et al. determined nonlinear molecular polarizabilities by measuring K in liquids as a function of temperature. 

Table 14 Theoretically calculated, and experimentally measured Kerr constants of some non-dipolar liquids (at room temperature)...

When an electric field is applied to a material, the induced birefringence is the difference between the index of refraction for directions parallel and perpendicular to the applied field [35], as measured by the Kerr constant. 

The Kerr constant around cf> v0.1 becomes very large for ATB microemulsions and the decay curve becomes exponential.The measured decay time t is in fairly good agreement with the lifetime tg of a critical density fluctuation of size . is the correlation length of the density fluctuations previously measured in ATB microemulsion by light scattering and 3... 

Ionization constants of hydroxy- and mercaptopyridazines, ° of amino- and diaminopyridazines and their quaternization products,of methylsulfinylpyridazines," and of pyridazinium ylides have been recorded. The basicities of a series of pyridazines have been determined and correlated with substituent constants using the Hammett free-energy relationship. The magnetic susceptibility of pyridazine was measured, and the rate constant for the reaction of hydrogen atoms with pyridazine was determined. The experimental dipole moment, Kerr constant, and molar Cotton-Mouton constant, obtained at 298 K and 633 nm, are reported. The magnetic circular dichroism spectrum of pyridazine has been measured. ... 

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... 

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