Polarization Raman spectra

The diffusion, location and interactions of guests in zeolite frameworks has been studied by in-situ Raman spectroscopy and Raman microscopy. For example, the location and orientation of crown ethers used as templates in the synthesis of faujasite polymorphs has been studied in the framework they helped to form [4.297]. Polarized Raman spectra of p-nitroaniline molecules adsorbed in the channels of AIPO4-5 molecular sieves revealed their physical state and orientation - molecules within the channels formed either a phase of head-to-tail chains similar to that in the solid crystalline substance, with a characteristic 0J3 band at 1282 cm , or a second phase, which is characterized by a similarly strong band around 1295 cm . This second phase consisted of weakly interacting molecules in a pseudo-quinonoid state similar to that of molten p-nitroaniline [4.298]. 

Since then, the vibrational spectrum of Ss has been the subject of several studies (Raman [79, 95-100], infrared [101, 102]). However, because of the large number of vibrations in the crystal it is obvious that a full assignment would only be successful if an oriented single-crystal is studied at different polarizations in order to deconvolute the crystal components with respect to their symmetry. Polarized Raman spectra of samples at about 300 K have been reported by Ozin [103] and by Arthur and Mackenzie [104]. In Figs. 2 and 3 examples of polarized Raman and FTIR spectra of a-Ss at room temperature are shown. If the sample is exposed to low temperatures the band-widths can enormously be reduced (from several wavenumbers down to less than 0.1-1 cm ) permitting further improvements in the assignment. 

Fig. 6 Polarized Raman spectra of the bending vibration Vg (big, b2g, b ) in a single crystal of a-Sg each showing the penetration of modes of other polarizations as weak shoulders, after [105]...

Polarized Raman spectra from the alkali fluorides LiF, NaF and CsF habe been observed with argon laser excitations by Evans and Fitchen 09). These spectra are of interest as an extreme test of lattice dynamics theories and polarizability models. 

The initial studies described above were conducted on Raman microspectrometers on extracted human teeth. In order to translate this research from the laboratory bench to the dental chair side, the next step it is to develop dedicated systems for clinical use. A key element to this development is the use of fibre-optic probes to allow measurements in vivo. We recently reported a study in which optical fibres were used for PRS measurements [48], Although not yet fully realized into a dental probe, this study demonstrated the design and feasibility of acquiring parallel- and cross-polarized Raman spectra via a bifurcated optical fibre whose distal terminal has the two fibres aligned vertically for simultaneously collecting spectra from the two polarization channels on a 2D CCD array. Simultaneous data acquisition will allow for more rapid measurement times in vivo. 

Additional source of information for UHMWPE acetabular cups arises from the quantitative analysis of polarized Raman spectra. Figure 17.6 shows photographs and the outcome of such analysis for two acetabular cups, which were retrieved after substantially different in vivo lifetimes. The retrieved acetabular cups were both belonging to male patients and sterilized by y-rays, but produced by different processes. One acetabular component (manufactured in 2002 by Biomet Inc.) was prepared by isostatic compression molding and sterilized before implantation by a dose of 33 kGy of y-rays. It was retrieved due to infection after 2 years 5 months. This cup will be referred to as the short-term retrieval. The other retrieval (manufactured in 1995 by Zimmer Inc.) was prepared by Ram-extruded molding and sterilized in air by a dose of 25-37 kGy of y-rays. For this latter cup, the follow-up pe-... 

Figure 2. Polarized Raman spectra at different temperatures for (a) an antiferromagnetic sample (Ml, S =0.071) and (b) a ferromagnetic sample (M5, <5 = 0.125).

For an example of the use of polarized Raman spectra of calcite single crystal, see Section 1.19. 

Figure 1-43 Polarized Raman spectra of calcite. (Reproduced with permission from Ref. 61.)...

The reasons for the less satisfactory agreement between the theoretical and experimental polarized Raman spectra may be both on the theoretical and on the experimental sides. The experimental polarized spectrum is obtained as the difference of two nearly equal signals excited with different beam polarizations 409 410, and the accuracy of the polarized intensities deduced from the experiment is rather poor. On the other hand, the theoretical values of the interaction-induced trace may suffer from the size-inconsistency of the cisd method or from the basis-set superposition error. 

Fig. 4.6.10. Polarized Raman spectra from approximately 1 n domain of the secondary wall in a longitudinal section of woody tissue a electric vector parallel to the cell wall b electric vector perpendicular to the wall...

Figure 4.8-22 Polarized Raman spectra of twin free single crystals of YBa2Cu307, according to McCarty et al., 1990.

Single crystal Raman spectra of 123 compounds have defined selection rules and prove that in unpolarized spectra Ag modes dominate. Fig. 4.8-22 shows polarized Raman spectra of these compounds. The strongest spectra are obtained with a (zz) scattering geometry, except for the as-0 2,3) mode at 340 cm, which has a nearly zero Raman tensor component in this direction. It is therefore occasionally referred to as quasi Big. 

Fig. 10.8 Polarized Raman spectra and depolarization ratios of benzenethiol under...

XeEs CeFs". Assignments for the XoFs ion in XeFs GeFs" are given in Table VII. In polarized Raman spectra recorded from a single crystal, the cation stretching hands that transform as Ag in the point group of the crystal (/)2 ) are most intense for the 1 polarization. The correlation D i, ... 

M. H. Proffitt and L. Frommhold. New measurement of the trace of the helium diatom polarizability from collision induced polarized Raman spectra. Phys. Rev. Lett., 42 1473-1475 (1979). 

Z.K. Tang, M.M. Loy, T. Goto, J.S. Chen, and R. Xu., Polarized Raman Spectra of Se Chains Isolated in Channels of AlP04-5 Single Crystal. Solid State Commun., 1997, 101, 333-336. 

V.V. Poborchii, A.V. Kolobov, J. Caro, V.V. Zhuravlev, and K. Tanaka., Polarized Raman Spectra of Selenium Species Confined in Nanochannels of AlP04-5 Single Crystals. Chem. Phys. Lett, 1997, 280, 17-23. 

T. Azuhata, T. Sota, K. Suzuki, and S. Nakamura, Polarized Raman spectra in GaN, J. Phys. Cond. Matter 7, L129-L133 (1995). 

In the preceding section, the 30 normal vibrations of the Bravais cell of calcite crystal have been classified into symmetry species of the factor group The results (Table 1.26) show that three intramolecular (A2m + 2 J, three translatory lattice (A2u + 2 ) and two rotatory lattice (A2 + vibrations are IR-active, whereas three intramolecular (Aig + 2Eg), one translatory lattice (Eg), and one rotatory lattice (Eg) vibrations are Raman-active. In order to classify the observed bands into these symmetry species, it is desirable to measure infrared dichroism and polarized Raman spectra using single crystals of calcite. 

Polarized Raman spectra provide more information about the symmetry properties of normal vibrations than do polarized infrared spectra [143]. Again consider a single... 

Fig. 2.27. Polarized Raman spectra of [(/i-C4H9)4N]2 [IrCle] in acetonitrile (488 nm excitation) [1273].

Fowler BO (1977) I. Polarized Raman spectra of apatites. II. Raman bands of carbonate ions in human tooth enamel. Mineralized Tissue Research Communications Vol 3, no. 68 Fratzl P, Fratzl-Zelman N, Klaushofer K, Vogl G, Roller K (1991) Nucleation and growth of mineral crystals in bone studied by small-angle X-ray scattering. Calcif Tissue Inti 48 407-413 Fratzl P, Schreiber S, Boyde A (1996) Characterization of bone mineral crystals in horse radius by small-angle X-ray scattering. Calcif Tissue Inti 58 341-346... 

Figure 22. Unpolarized Raman spectra of single-crystal KNCS and (xz) polarized Raman spectra of single-crystal KN3, at different temperatures. A spectral slit width of 4-5 cm was used for the measurements. Peaks marked m in the low-temperature spectrum of KNCS are probably due to two-phonon combinations.

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