Raman scattering depolarization ratios

TABLE 1 Depolarized Raman scattering intensity ratio of G BAND and RBM bands in VV configuration (0 = 0°, 90°) versus VH configuration at 0 = 0° for as-spun and 5x dribrefibers of PAni-Es/AMPSA-SWNT (0.76 %w/w)... 

The Raman spectrum can be used to give additional information regarding the symmetry properties of vibrations. This information derives from the measurement of the depolarization ratio p for each Raman band. The quantity p is a measure of the degree to which the polarization properties of the incident radiation may be changed after scattering... 

A frequency job begins by computing the energy of the input structure. It then goes on to compute the frequencies at that structure. Gaussian predicts the frequencies, intensities, and Raman depolarization ratios and scattering activities for each spectral line ... 

Raman scattering activities (A 4/AMU), Raman depolarization ratios. 

It is important from a practical viewpoint to predict the shear viscosity of mixtures from those of pure melts. For alkali nitrate melts, a linear dependence has been found between the reorientational line width obtained by Raman measurements and the ratio of temperature divided by shear viscosity.For NO3 ions, the depolarized Raman scattering from 1050cm" total stretching vibrational mode (Al) has a contribution to the line width L, which is caused by the reorientational relaxation time of the Csv axis of this ion. The Stokes-Einstein-Debye(SED) relation establishes a relation between the shear viscosity r of a melt and the relaxation time for the reorientation of a particle immersed in it ... 

Cyvin, S. J., Rauch, J. E. and Decius, J. C. (1965) Theory of hyper-Raman effects (nonlinear inelastic light scattering) selection rules and depolarization ratios for the second-order polarizability. 

Vibrational Raman Scattering of radiation with changed frequency due lo polarizability change during a vibration (A = visible usually) Qualitative for large molecules 10-Ms 10 Pa (100 ion) (v dependent) Useful for characterization. Some structural information from number of bands, position, depolarization ratios, and possibly Isotope effects. All... 

In addition to the intensity and frequency of the Raman lines, the polarization character of the lines can be measured. In fact, what led Sir C. V. Raman to believe that he was observing a new phenomenon was the unique polarization properties of this new radiation. Usually, the observations are made perpendicular to the incident beam, which is plane-polarized, as at (a) in Fig. 15. The depolarization ratio p is defined as the intensity ratio of the two polarized components of the scattered light that are respectively parallel and perpendicular to the direction of the (polarized) incident beam when the polarization of the incident beam is perpendicular to the plane of propagation and observation (p = I /ll). 

Raman scattering activities (A 4 /AMU), Raman depolarization ratios, reduced masses (AMU), force constants (mDyne/A) and normal coordinates ... 

For a purely isotropic Raman scattering tensor, the depolarization ratio will be zero since the scattered light from such a system must have a polarization parallel to the incident beam. This is evident when equation equation (5.29) is used in equation (5.30) so that [21],... 

Besides being always Raman active, the totally symmetric vibrational modes can also be readily identified in the spectrum. As shown in Fig. 7.3.2, the scattered Raman radiation can be resolved into two intensity components, /l and 7. The ratio of these two intensities is called the depolarization ratio p ... 

As stated in the preceding section, depolarization ratios of Raman bands provide valuable information about the symmetry of a vibration that is indispensable in making band assignments. Figure 1-18 shows a coordinate system which is used for measurements of depolarization ratios. A molecule situated at the origin is irradiated from the y-direction with plane polarized light whose electric vector oscillates on the yz-plane (Ez). If one observes scattered radiation from the x-direction, and measures the intensities in the... 

The differential Raman scattering cross sections and depolarization ratios in the Fermi resonance region of carbon disulphide CS2 were measured and interpreted in terms of three bond polarizability parameters and the cubic force constant k 22 (Montero et al., 1984). 

The depolarization ratio in Raman scattering has no true counterpart in IR absorption. However, the dipole moment is... 

Type of Raman scattering Vibrational band character Polarizability tensor symmetry Depolarization ratio... 

Polarized analysis There is useful spectral information arising from the analysis of polarization of Raman scattered light. This, typically called as polarized analysis, provides an insight into molecular orientation, molecular shape, and vibrational symmetry. One can also calculate the depolarization ratio. Overall, this technique enables correlation between group theory, symmetry, Raman activity, and peaks in the corresponding Raman spectra. It has been applied successful for solving problems in synthetic chemistry understanding macromolecular orientation in crystal lattices, liquid crystals or polymer samples and in polymorph analysis. 

M. Fairbanks, R. L. McGreevy, and E. W, J. Mitchell. Depolarization ratios for Raman scattering from molten alkali and alkali-earth halides. J. Phys. Chem., 79 L53-L58 (1986). 

The Gas Phase Polarizability Anisotropy. Murphy50 has measured the depolarization ratio for Rayleigh scattering, pR, and analysed the intensity distribution in the rotational Raman spectrum of the vapour at 514.5 nm. The ratio R20 of the invariants of the a,-,aA/ tensor can be determined by fitting the rotational Raman distribution, and a is known (from the Zeiss-Meath formula). Knowledge of the three quantities, a, pR and R2o, allows the polarizability anisotropy, Aa, and the three principal values of the tensor to be calculated. The polarizability anisotropy invariant is numerically equal to the quantity,... 

A knowledge of the frequency-dependent polarizability functions and their gradients allows the Raman scattering cross sections and depolarization ratios... 

Finally, M is introduced for convenience and represents the integral function of polarizability. It is the only function, the value of which depends on the polarizability characterizing the scattering medium. /iso( u) Raman spectrum depends only on the vibration motion and /aniso( y) depends on both vibration and reorientation motions of the molecule. In addition to the familiar qualitative use of the depolarization ratio, P = - Hv/. vv, to identify symmetric modes (i.e. p < 0.75), the quantitative studies of /iso and /aniso may provide detailed information about the vibration and reorientation relaxation. 

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