Absorption dissymmetry ratio

A = absorbance c = concentration d = path length / = frequency 1,5 = absorption dissymmetry ratio glujjj = luminescence dissymmetry ratio I = light intensity J = total angular quantum number t = time = extinction coefficient A = wavelength a = standard deviation. 

Mixed solvents are generally unsatisfactory for use in the determination of polymer molecular weights owing to the likelihood of selective absorption of one of the solvent components by the polymer coil. The excess of polarizabilit f of the polymer particle (polymer plus occluded solvent) is not then equal to the difference between the polarizabilities of the polymer and the solvent mixture. For this reason the refractive increment dn/dc which would be required for calculation of K, or of i7, cannot be assumed to equal the observed change in refractive index of the medium as a whole when polymer is added to it, unless the refractive indexes of the solvent components happen to be the same. The size Vmay, however, be measured in a mixed solvent, since only the dissymmetry ratio is required for this purpose. 

Tn the critical region of mixtures of two or more components some physical properties such as light scattering, ultrasonic absorption, heat capacity, and viscosity show anomalous behavior. At the critical concentration of a binary system the sound absorption (13, 26), dissymmetry ratio of scattered light (2, 4-7, II, 12, 23), temperature coefficient of the viscosity (8,14,15,18), and the heat capacity (15) show a maximum at the critical temperature, whereas the diffusion coefficient (27, 28) tends to a minimum. Starting from the fluctuation theory and the basic considerations of Omstein and Zemike (25), Debye (3) made the assumption that near the critical point, the work which is necessary to establish a composition fluctuation depends not only on the average square of the amplitude but also on the average square of the local... 

The extra factor of 1/2 in this equation results from the fact that the equivalent expression for the absorption dissymmetry factor (or ratio), gabs > employed in CD spectroscopy is defined in terms of the difference in extinction coefficients, Ae, divided by the average extinction coefficient, e. 

Absorption (gabs) luminescence (gium) dissymmetry ratios for selected transitions of a chiral crystal of... 

Measurement of CPL from racemic mixtures is not a technique that can be applied to all racemic solutions. For moderately luminescence systems values of approximately 10 are measurable. This means that the intrinsic absorption and emission dissymmetry ratios need to be on the order of 10 for this experiment to be successful. Although there have been a couple of examples using this technique in organic systems, by far the most widely studied systems are racemic lanthanide complexes, such as given in Figure 5, because of the large and g bs values that may exist for certain f o f transitions. It is also useful to perform these experiments in a time-resolved mode and as a function of temperature to determine racemization rate constants. 

The ratio between As and e at a given wavelength yields the absorption dissymmetry factor ... 

The ratio of the circular dichroism signal and the corresponding absorption is called dissymmetry factor g ... 

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