Raman intensity distribution

Figure 2.7 (a) Tip-enhanced near-field Raman spectral mapping ofthe adenine nanocrystal at 30 nm intervals, (b) Raman intensity distribution of two major bands at 739 cm and 1328cm. ... 

Using the calculated phonon modes of a SWCNT, the Raman intensities of the modes are calculated within the non-resonant bond polarisation theory, in which empirical bond polarisation parameters are used [18]. The bond parameters that we used in this chapter are an - aj = 0.04 A, aji + 2a = 4.7 A and an - a = 4.0 A, where a and a are the polarisability parameters and their derivatives with respect to bond length, respectively [12]. The Raman intensities for the various Raman-active modes in CNTs are calculated at a phonon temperature of 300K which appears in the formula for the Bose distribution function for phonons. The eigenfunctions for the various vibrational modes are calculated numerically at the T point k=Q). 

Chew and Wang(39) have pointed out the possibility of double resonance, that is, that the frequencies of both the excitation and inelastically scattered radiation are resonant. They presented the results of calculations which indicate that double resonance can have a significant effect on the angular intensity distribution of inelastically scattered radiation. This case is of some practical interest, particularly in Raman studies, where coincidence may lead to anomalous Raman band intensities, if both the excitation and the shifted frequency are resonant. 

Raman spectra of adsorbed species, when obtainable, are of great importance because of the very different intensity distributions among the observable modes (e.g., the skeletal breathing frequency of benzene) compared with those observed by infrared spectroscopy and because Raman spectra of species on oxide-supported metals have a much wider metal oxide-transparent wavenumber range than infrared spectra. Such unenhanced spectra remain extremely weak for species on single-crystal surfaces, but renewed efforts should be made with finely divided catalysts, possibly involving pulsed-laser operation to minimize adsorbate decomposition. Renewed efforts should be made to obtain SER and normal Raman spectra characterizing adsorption on surfaces of the transition metals such as Ni, Pd, or Pt, by use of controlled particle sizes or UV excitation, respectively. 

Another spectrum from a n complex has been observed by SERS following the adsorption of propene on cold-evaporated Ag (229). The intensity distribution, as expected for a Raman spectrum, is different from that in the infrared spectrum, but it does show readily observed features at 1612 and 1300 cm-1 from the coupled vC=C and <5=CH2 modes (1557 and 1267 cm-1 on Cu). As the corresponding absorptions on Pt or Ni are expected to be at notably lower wavenumbers than on Cu or Ag, and as no absorptions are discernible between 1550 and 1460 cm-1 in the spectra on the group VIII metal surfaces, this negative result reinforces the view that n species are not abundant on the latter catalysts. A recent theoretical study by Delbecq and Sautet (252) has, in agreement, concluded that for propene on Pt(lll) the n species is less stable with respect to di-cr than is the case for ethene on Pd(l 11) the difference was much less marked. More low- and room-temperature studies of propene on several Al203-supported metals are needed to obtain reliable information about the nonpropylidyne species. 

Mizutani and Kitagawa measured the time-dependent Stokes and anti-Stokes Raman intensities of the heme v4 band after photoexcitation and used the relative intensities to estimate its temperature and thermal relaxation dynamics (30). They found the population relaxation to occur biexponen-tially with 1.9 ps (93%) and 16 ps (7%) time constants. The dominant 1.9 ps population relaxation correlates with a 3.0 ps thermal relaxation, which is a factor of 2 faster than the ensemble averaged temperature relaxation deduced from the near-IR study of band III. The kinetic energy retained within a photoexcited heme need not be distributed uniformly among all the vibrational degrees of freedom, nor must the energy of all vibrational modes decay at the same rate. Consequently, a 6.2 ps ensemble-averaged estimate of the heme thermal relaxation is not necessarily inconsistent with a 3 ps relaxation of v4. 

D mapping of a sample may be achieved with an x - y drive which transports the sample at the focal region of the spectrometer or the microscope (Fig. 3.5-10 a, b Schrader, 1990). If fiber optics is employed, the fiber head may be moved while the sample remains stationary. For each resolved sample point, a spectrum may be recorded and stored. A map showing the intensity distribution of different Raman lines illustrates the distribution of specific compounds over the surface. 

The intensity distribution in the rotational Raman spectra of the linear molecules CO2 and N2O which are partly excited to the 01 O vibrational level at room temperature... 

The 27-cliads in the vibrational Raman spectrum of CO2 and its isotopic variants were measured and their intensity distribution simulated (Srinivasan et al., 1977 Finsterholzl et al., 1978 Kldckneret al., 1978 Finsterholzl, 1982 Wienecke et al., 1986). In Fig. 4.3-25 the experimental and the calculated Raman spectra of natural CO2 in the Fermi resonance region are presented, the lowest (calculated) spectrum showing only the 2-branches of the Fermi doublet of C 02 and its hot bands and those of the isotopomers C 02, and occuming in natural abundances of 1.1 %, 0.4 %, and 0.08 %,... 

Rotational temperature from the intensity distribution in purely rotational Raman spectra... 

S.4.2 Determining the vibrational temperature from the intensity distribution of vibrational-rotational Raman bands... 

A comparison of the UV Raman spectrum measured for coke deposited during the MTH reaction with that deposited during butane dehydrogenation catalyzed by chromia on alumina (66) shows clear differences in the spectral intensity distribution (Fig. 11). In particular, the intensity of the features in the regions 1340-1440cm and 1560 1630 cm are nearly equal for the MTH reaction. 

Fig. 11.10 A representative imaging scheme using SERS multiplexing, (a) A general concept scheme. Distribution of several targets can be imaged from a single scan by Raman intensity mapping of specific SERS band of each SERS tag, and (b) an example by Woo et al. [71]. The three different SERS intensity maps correspond to distributions of CD34, Sca-1, and SP C proteins on tissue sample. They were obtained by single scan at the pre-selected area...

It is noted that the phonon wavefunction is a superposition of plane waves with q vectors centered at In the literature, several weighting functions such as Gaussian functions, sine, and exponential functions have been extensively used to describe the confinement functions. The choice of type of weighting function depends upon the material property of nanoparticles. Here, we present a brief review about calculated Raman spectra of spherical nanoparticle of diameter D based on these three confinement functions. In an effort to describe the realistic Raman spectrum more properly, particle size distribution is taken into account. Then the Raman intensity 7(co) can be calculated by ... 

The Gas Phase Polarizability Anisotropy. Murphy50 has measured the depolarization ratio for Rayleigh scattering, pR, and analysed the intensity distribution in the rotational Raman spectrum of the vapour at 514.5 nm. The ratio R20 of the invariants of the a,-,aA/ tensor can be determined by fitting the rotational Raman distribution, and a is known (from the Zeiss-Meath formula). Knowledge of the three quantities, a, pR and R2o, allows the polarizability anisotropy, Aa, and the three principal values of the tensor to be calculated. The polarizability anisotropy invariant is numerically equal to the quantity,... 

Figure 5.10 (a, d) Fluorescence images (using intensities of DNA-specific bands of the cells DAPI stain) of the chromatin distribution of shown in (a) and (d) (c, f) Distribution of the HeLa cells in metaphase (a) and anaphase Raman intensities of protein bands of the (d). The cell in (a) measures ca. 25pm cells shown in (a) and (d). 

---