Raman peak

The force effect is applicable to investigation of the mechanical properties of nanomaterials [28, 29]. We measured TERS spectra of a single wall carbon nanotube (SWCNT) bundle with a metallic tip pressing a SWCNT bundle [28]. Figure 2.13a-e show the Raman spectra of the bundle measured in situ while gradually applying a force up to 2.4 nN by the silver-coated AFM tip. Raman peaks of the radial breathing... 

Table II). Representative TR spectra at three different wave- lengths are shown in Figure 7. It is seen that all of the "bpy " Raman peaks show greatly increased intensity with short excitation wavelength, while the "neutral bpy" peaks increase in rela-tive intensity at the long excitation wavelength. Three of the "bpy " modes in the excited state also show long-wavelength enhancement, and these are analogous to three modes of chemically reduced bipyridine radical anion which are also enhanced with long-wavelength excitation (53).

The Raman modes yC=C and v =C depend on chain length in a manner which parallels the absorption energy dependence on chain length (25). The contribution of each chromophore to the observed Raman peak is determined by the RS intensity for incident light at energy The RS peak position is then a weighted average of all... 

Fig. 18.8 SERS detection in LC ARROW, (a) Top view of experimental beam geometry excitat ing rhodamine 6G molecules bound to silver nanoparticles (leyLC) excitation beam, 1R Raman signals) (b) R6G concentration dependent SERS power for three representative Raman peaks PI P3, inset spectra at various excitation powers...

An interesting and powerful new development in Raman spectroscopy of catalysts is the use of a UV laser to excite the sample. This has two major advantages. First, the scattering cross section, which varies with the fourth power of the frequency, is substantially increased. Second, the Raman peaks shift out of the visible region of the spectrum where fluorescence occurs. The reader is referred to Li and Stair for applications of UV Raman spectroscopy on catalysts [40]. 

Raman Peaks Observed in MoS2 Nanoparticle Spectra at Room Temperature and the Corresponding... 

Fig. 49. The levitation voltage and the Raman peak height associated with the C—Br bond for the chemical reaction between 1-octadecene and bromine (from Buehler, 1991).

Figure 5. V4 Raman peaks for a stationary sample of NiTPP (0.2n ) in pyridine, with 406.7nm excitation. Arrows indicate the decreasing (1346cm ) and increasing (1369cm"l) relative band intensities at increasing laser power levels (1.5, 5, 10,...

The comparison of PTCDA with its parent perylene molecule is extremely interesting. For perylene MLs on Ag(l 11), electron diffraction suggests an orientational liquid, in which the molecules are positionally ordered in an incommensurate close-packed superlattice but orientationally disordered and mobile. The same activated Raman peaks as for PTCDA are observed but they are, however, orders of magnitude weaker, indicating that, while a molecular reaction centre may still exist in the perylene backbone, its residual activity would be too small for the molecule to recognize a preferred site. 

FIGURE 10.6 TERS spectra of (a) Rhodamine 6G, (b) Crystal Violet, and (c) aggregates of Rhodamine 6G and Crystal Violet. The Raman peaks at A and B were employed for TERS imaging. 

There are differences between the kinds of groups that absorb in the IR and those that are Raman active. Parts of Raman and IR spectra are complementary, each being associated with a different set of vibrational modes within a molecule. Other vibrational modes may be both Raman and IR active. The intensity or power of a Raman peak depends in a complex way on the polarizability of the molecule, the intensity of the source, and the concentration of the active group, as well as other factors. Raman intensities are usually directly proportional to the concentration of the active species. 

Raman scattering in water is used as a sensitivity test for fluorimeters. The test consists of measuring the signal to noise ratio of the Raman peak using a cell filled with water. For example, signal/noise will be measured at 397 nm (25191 cm1) if the excitation energy used is 350 nm (28571 cm 1). 

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