Raman band

An interesting phenomenon called the noncoincidence effect appears in the Raman spectroscopies. This is seen when a given Raman band shows a peak position and a bandwidth that differs (slightly) with the... 

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... 

Large Specific Surface Area Porous materials can have a large proportion of surface atoms - their surface area within a typical sampling volume of 10 pm can reach 10 pm, which is approximately 10 larger than for a smooth surface crossing the same volume. These effects lead to clearly increased Raman intensities of surface species and also to improved intensity ratios of surface and bulk Raman bands. 

In Raman spectroscopy the intensity of scattered radiation depends not only on the polarizability and concentration of the analyte molecules, but also on the optical properties of the sample and the adjustment of the instrument. Absolute Raman intensities are not, therefore, inherently a very accurate measure of concentration. These intensities are, of course, useful for quantification under well-defined experimental conditions and for well characterized samples otherwise relative intensities should be used instead. Raman bands of the major component, the solvent, or another component of known concentration can be used as internal standards. For isotropic phases, intensity ratios of Raman bands of the analyte and the reference compound depend linearly on the concentration ratio over a wide concentration range and are, therefore, very well-suited for quantification. Changes of temperature and the refractive index of the sample can, however, influence Raman intensities, and the band positions can be shifted by different solvation at higher concentrations or... 

Nitrophenyl groups covalently bonded to classy carbon and graphite surfaces have been detected and characterized by unenhanced Raman spectroscopy in combination with voltammetry and XPS [4.292]. Difference spectra from glassy carbon with and without nitrophenyl modification contained several Raman bands from the nitrophenyl group with a comparatively large signal-to-noise ratio (Fig. 4.58). Electrochemical modification of the adsorbed monolayer was observed spectrally, because this led to clear changes in the Raman spectrum. 

These nested nanotubes may be harvested from the core by grinding and sonication nevertheless, substantial fractions of other types of carbon remain, all of which are capable of producing strong Raman bands... 

NMR and visible spectra have established that a number of S-N anions are present in such solutions.The primary reduction products are polysulfides Sx, which dissociate to polysulfur radical anions, especially the deep blue 83 ion (/Imax 620nm). In a IM solution the major S-N anion detected by NMR spectroscopy is cycZo-[S7N] with smaller amounts of the [SSNSS] ion and a trace of [SSNS]. The formation of the acyclic anion 5.23 from the decomposition of cyclo-Sjl is well established from chemical investigations (Section 5.4.3). The acyclic anions 5.22 and 5.23 have been detected by their characteristic visible and Raman spectra. It has also been suggested that a Raman band at 858 cm and a visible absorption band at 390 nm may be attributed to the [SaN] anion formed by cleavage of a S-S bond in [SSNS]. ° However, this anion cannot be obtained as a stable species when [SsN] is treated with one equivalent of PPhs. 

The intensity of a Raman band in the harmonie approximation is given by the derivative of the polarizability with respect to a normal coordinate. 

Breuillard C., Ouillon R. Infrared and Raman band shapes and dynamics of molecular motions for N20 in solutions v3 band in CCL and liquid SF6. Mol. Phys. 33, 747-57 (1977). 

May A. D., Stryland J. C., Varghese G. Collisional narrowing of the vibrational Raman band of nitrogen and carbon monoxide, Can. J. Phys. 

Le Duff Y. Raman band shape of the N2 molecule dissolved in liquids, J. Chem. Phys. 59, 1984-7 (1973). 

Le Duff Y., Holzer W. Raman band shapes of small diatomic molecules dissolved in inert liquids, Chem. Phys. Lett. 24, 212-16 (1974). 

As illustrated by the spectra of P. furiosus 3Fe Fd shown in Fig. 8, the relative intensities of the Raman bands for [Fe3S4l clusters vary considerably with excitation wavelength. However, because of the extensive mixing of Fe-S and Fe-S modes, excitation profiles in the region 400-650 nm appear to be of little use in effecting electronic... 

Raman spectroscopy of matrix-isolated molecules carries some difficulties conneeted with the possibility of local heating of the matrix under laser irradiation. Besides, because of the relatively low intensity of Raman bands, higher concentrations of the species to be studied are needed in the matrix (the ratio of matrix gas to reagent = 100-500). As a result, the effective isolation of reactive intermediates is prevented. 

Raman Band Positions (cm ) IR Band Positions (cm ) Assignments... 

Figure 3. Frequency shift of the Raman band at 612 cm for Fe-TsPc adsorbed on a sliver electrode as a function of the applied potential vs. SCE In 0.05 M H2S0. Laser excitation line 514.5 nm potential sweep rate 10 mV s electrode area 0.27 cm. See caption Fig. 2.

Figure 4. Intensity as a function of potential vs. SCE for two of the Raman bands (1346 cm and 699 cm ) of Fe-TsPc adsorbed on a silver electrode at different pH values. These measurements were obtained at a potential scan rate of 10 mV s. See caption Fig. 2.

In this section, we will describe some experiments which we have performed using the above-mentioned nano-Raman microscope. Figure 2.6a shows the Raman spectmm of an adenine nanocrystal of height 7 nm and width 30 nm [19]. Several Raman bands are observed as the probe tip is near enough to the sample (AFM operation is made in contact mode). These bands, except the one appearing at 924 cm, are assigned as the vibrational modes, inherent to the adenine molecule, according to the molecular orbital calculation. For examples, two major bands, one at... 

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