Depolarization of scattered light

Flory has recently summarized the experimental evidence pertaining to local correlation and their effects on chain dimensions (49). There is experimental support for local alignment from optical properties such as stress-optical coefficients in networks (both unswelled and swelled in solvents of varying asymmetry), and from the depolarization of scattered light in the undiluted state and at infinite dilution. The results for polymers however, turn out to be not greatly different from those for asymmetric small molecule liquids. The effect of... 

Here, a. and a L are the polarizabilities of the diatom parallel and perpendicular to the internuclear separation, R12. The electrostatic theory accounts for the distortions of the local field by the proximity of a point dipole (the polarized collisional partner) and suggests that the anisotropy is given by ft Rn) 6intermolecular interactions). This is the so-called dipole-induced dipole (DID) model, which approximates the induced anisotropy of such diatoms often fairly well. It gives rise to pressure-induced depolarization of scattered light, and to depolarized, collision-induced Raman spectra in general. 

Orientation polarization Depolarization of scattered light (All results negative)... 

This valency angle is no new idea in organic chemistry. The essential fact is that this angle is now obtained directly for the first time by means of vector combination of the moments. Hitherto, however, it has only been possible to carry out these calculations for a few substances. Hence the fact is of importance that (as I shall show by means of one or two examples) the depolarization of scattered light and the Kerr effect enable us to prove the existence of such angles and to calculate their value, even when free rotation, which gives rise to errors in the vectorial combination, is present. 

Interpretation of the Second Osmotic Virial Coefhcient Depolarization of Scattered Light Polydisperse Samples Turbidimetry... 

The methods of the Kerr effect and the depolarization of scattered light have not so far been applied to the realm of high polymers, but it is conceivable that by their aid it will be possible to obtain data for relatively complex molecules on the symmetry and form of the particles and on the position of substituents. It should, of course, be emphasized that both methods are particularly sensitive to molecular interaction and they should therefore be applied as far as possible to the gaseous state or to that of dilute solution. 

Cabannes factor analy chem An equational factor to correct for the depolarization effect of the horizontal components of scattered light during the determination of molecular weight by optical methods. ko banz. fak-tor cacodyl orgchem (CH3)2As A radical found in, for example, cacodylic acid, (CH3)2A-sOOH. kak-3 dil ... 

If we now proceed to consider those mono- and di-substituted benzene derivatives in which as a good approximation we may assume the existence of rotational symmetry, as is shown by the values of the depolarization factor of scattered light differing only slightly from the values for benzene, we have the following state of affairs. 

R. L. Rowell, G. M. Aval, and J. J. Barrett. Rayleigh-Raman depolarization of laser light scattered by gases. J. Chem. Phys., 54 1960-1964 (1971)... 

Additional information about the vibration can be obtained through the depolarization ratio. This is the ratio of the intensity of scattered light that is polarized in a plane perpendicular to the incident radiation relative to that the scattered light that is polarized parallel to the incident polarization, p = For totally symmetric modes, p = 0, while 0 < p < 3/4 for non-totally symmetric modes [i, 3]. The polarization ratio can actually be greater than 3/4 for a resonantly enhanced Raman band [3]. 

In the case of a molecule that is free to explore a wide range of orientations rapidly, compared with the lifetime of the excited state, the emission will be essentially depolarized and r = 0 since fy = However, if the molecule experiences some degree of hindered rotation or alignment, r will be non-zero. For completely polarized light, for example scattered polarized laser light, r = 1. Note that the absorption and emission dipoles for typical fluorophores are never perfectly parallel and so some degree of depolarization is intrinsic even for a rota-tionally frozen molecule (hence the use of scattered light in this example). 

Let the direction of propagation of the incident radiation be the z axis and the direction of observation be perpendicular to the z axis in the xy plane (see Fig. 1.33). The depolarization ratio p is defined as the ratio of the intensity of scattered light polarized perpendicular to the xy plane /j to that polarized parallel to the xy plane /.i. 

Characterization of their stmcture and properties is essentially the same as that for ordinary particles, but the important difference is that they are usually binary- or multicomponent particles, having internal microstmctures and even showing some degree of order. The multicomponent treatments described in Sections 2.10.2.3.1 and 2.10.2.3.3 are applicable, and, in some cases, the depolarized component of scattered light could be useful for further characterization. 

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