Band assignments, Raman spectroscopy

Chalcogenometalate ions are distinguished by characteristic high-intensity absorption bands in the UV-vis region but they can also be traced by IR and Raman spectroscopy. Total assignments and normal coordinate analyses are available for many of the species (also with recourse to isotope shifts, as in the case of MoOjSj-, 92/100MoOS2 or 92,100MoS4-). 

OxyHr is purple in color, associated with a X as near 500 nm, which is polarized perpendicular to the Fe-Fe axis in single-crystal absorbance data (98, 99). Resonance Raman spectroscopy unequivocally assigns this electronic spectral feature to a peroxide-to-Fe(III) charge-transfer band (137-139). Vibrational features at 503 and 884 cm are assigned to v(Fe-02) and v(O-O), based on their sensitivity to substitution. Their enhance-... 

Polarization effects are another feature of Raman spectroscopy that improves the assignment of bands and enables the determination of molecular orientation. Analysis of the polarized and non-polarized bands of isotropic phases enables determination of the symmetry of the respective vibrations. For aligned molecules in crystals or at surfaces it is possible to measure the dependence of up to six independent Raman spectra on the polarization and direction of propagation of incident and scattered light relative to the molecular or crystal axes. 

The complex structure of the various solutions was investigated by Raman and IR absorption spectroscopy. Containers made of sapphire and KRS-5 were used for Raman and IR spectra measurements, respectively. Vibration spectra analysis was performed based on the band assignment [171, 187] presented in Table 45. 

The first Raman and infrared studies on orthorhombic sulfur date back to the 1930s. The older literature has been reviewed before [78, 92-94]. Only after the normal coordinate treatment of the Sg molecule by Scott et al. [78] was it possible to improve the earlier assignments, especially of the lattice vibrations and crystal components of the intramolecular vibrations. In addition, two technical achievements stimulated the efforts in vibrational spectroscopy since late 1960s the invention of the laser as an intense monochromatic light source for Raman spectroscopy and the development of Fourier transform interferometry in infrared spectroscopy. Both techniques allowed to record vibrational spectra of higher resolution and to detect bands of lower intensity. 

Resonance Raman Spectroscopy as a Complement to Other Techniques for Making Electronic Band Assignments for (Re2X8)2 Ions... 

Raman spectroscopy is one of the most powerful techniques for the characterization of nanocarbons. It is also a convenient technique because it involves almost no sample preparation and leaves the material unharmed. There are four characteristic bands for CNTs The band at 200 cm-1 is called radial breathing mode (RBM). It depends on the curvature and can be used to calculate the diameter of SWCNTs [61]. The relatively broad D-band at 1340 cm-1 is assigned to sp2-related defects and disorder in the graphitic structure of the material. The tangential C-C stretching mode is located at -1560 cm 1 (G-band). The second order mode of the D-band can be observed (G -band,... 

In liquid ammonia, Raman spectroscopy indicated that the major species present was the tetraammine.24 This was based on the observation that the band assigned as y(N—Ag—N)Sym at 370 cm-1 in aqueous solutions was absent in liquid ammonia, whilst a new band occurred at 290cm-1. Also, whilst no tetraammine salts have been isolated from aqueous solution, recrystallization of [Ag(NH3)2]C104 from liquid ammonia yielded [Ag(NH3)4]C104. 

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