Raman scattering anisotropic

Temkin S. I., Burshtein A. I. On the shape of the Q-branch of Raman scattering spectra in dense media. Anisotropic scattering, Chem. Phys. Lett. 66, 62-4 (1979). 

Ikeda, K, Takase, M., Sawai, Y, Nahika, H., Murakoshi, K. and Uosaki, K. (2007) Hyper-Raman scattering enhanced hy anisotropic dimer plasmons on artificial nanostructures./. Chem. Phys., 127, 111103/1-111103/4. 

Figure 3. Calculated band profiles of Stokes vibrational Raman scattering from Nt at 2000 K assuming a triangular slit function with FWHM = 5.0 cm 1. The bottom curve includes the isotropic part of the Q-branch only. The top curve is a more exact calculation including O- and S-branch scattering, the anisotropic part of the Q-branch and line-strength corrections owing to centrifugal distortion. The base lines have been shifted vertically for clarity.

Ordinary Raman scattering intensity (far from resonance) can be expressed in terms of two invariants the isotropic transition polarizability a, and the anisotropic transition polarizability... 

Ikeda K, Takase M, Sawai Y, Nabika H, Murakoshi K, Uosaki K (2007) Hyper-Raman scattering enhanced by anisotropic dimer-plasmons on artificial nanostmctures. J Chem Phys 127 111103... 

Inner G, Brumme T, Herms M, Wernicke T, Kneissl M, Weyers M (2008) Anisotropic strain on pnonons in a-plane GaN layers studied by Raman scattering. J Mater Sci Mater Electron 19 S51-S57... 

M. S. Brown, M. H. Proffitt, and L. Frommhold. Collision induced Raman scattering by anisotropic molecules, Hj and Dj. Chem. Phys. Lett., In-.ld i-lAb (1985). 

The temperature dependence on the IR absorption and Raman scattering bandwidths of some fundamental modes of Aj, B, and B2 symmetries of thiophene has been investigated in the region 400-1600 cm <81CPH251>. The spectroscopic study was carried out in the liquid phase which requires simultaneous investigation of the bands. Results show that the IR and anisotropic Raman bandwidths increase with increasing temperature and more so in the latter case. The rotational diffusion coefficients obtained from the bandwidths indicate that the rotational and vibrational relaxation phenomena occur simultaneously. The IR and isotropic and anisotropic Raman band profiles of the Aj symmetry mode have also been studied in the liquid phase <81CPH265>. 

Raman scattering provides a nice way to gather information on these processes. For liquid samples, it is possible to separate experimentally the isotiopic spectrum (ISOT) from the anisotropic one (ANIS), namely... 

Isotropic and anisotropic Raman scattering contributions due to non-vanishing a ° (A,t) and a (A,t) occur frequency shifted by from the laser frequency. 

The depolarization ratio varies from zero for Raman scattering from totally symmetric modes where only the isotropic invariant is nonzero, through 3/4 for nontotally synametric modes in the case where only the synunetric anisotropic invariant is nonzero, and on to 00 for modes where only the antisymmetric anisotropic invariant is nonzero. It can be shown that the antisymmetric anisotropic invariant can be nonzero only for resonance Raman scattering. 

The theory of Raman scattering simplifies dramatically in the far-from-resonance (FFR) limit, where the exciting laser radiation is far from the lowest allowed excited electronic state of the molecule [15]. In this limit, the interaction of the light with the molecule is approximately the same for both the incident and the scattered radiation. There, the Raman tensor becomes symmetric and this symmetry reduces the number of Raman invariants from three to two, the isotropic and (symmetric) anisotropic invariants. The antisymmetric anisotropic invariant vanishes, by its antisymmetric definition in Eqs. (7) and (9), and we have... 

A new technique to measure low-frequency spectra is optical-heterodyne-detected Raman-induced Kerr-effect spectroscopy (OHD-RIKES). A recent publication by Chang and Cast-ner contains references to previous work within this field [18]. OHD-RIKES is based on a four-wave mixing of femtosecond laser pulses. Spectra obtained by OHD-RIKES reflect the anisotropic part of the Raman polarizability. Thus, the information obtained by OHD-RIKES is very similar to that obtained by low-frequency Raman scattering in an scattering configuration. From a theoretical point of view, the spectral representation obtained from OHD-RIKES measurements corresponds to the I v) representation given in Eq. (3). In Fig. 4 is shown an OHD-RIKES spectrum of liquid A-methylformamide (NMF). In Fig. 5 are shown low-frequency Raman spectra of liquid NMF together with the R(i>),... 

Any molecular property which is anisotropic, i.e., that shows a direcional dependence, is per se capable of providing information on orientation both in solids and in appropriate melts or liquids. Such properties include optical birefringence, infrared polarization, anisotropic Raman scattering, broad line NMR and X-ray diffraction, each of which has been exploited in the study of polymers. These various approaches yield differing amounts of information, for fundamental reasons in order to appreciate why this is so it is necessary to consider their theoretical basis, and also to have a convenient mathematical framework by which to quantify degrees of orientation. These two topics will now... 

---