Raman scattering coefficients

These equations have been employed for the determination of absolute Raman scattering coefficients of crystal powders (D Orazio and Schrader, 1974, 1976). Experiments have confirmed the consequences of this theory (Klosowski and Steger, 1979). 

In this context, the Raman scattering coefficient s is assumed to be equal for all samples. Only relative intensities of the Raman spectrum are discussed. 

Fig. 3.5-13 demonstrates the influence of sample and instrumental parameters on the intensities of the observed Raman lines, excited with the Nd YAG laser at 1064 nm. The lower abscissa shows the absolute wavenumber scale, the upper abscissa represents the Raman shift. The relative intensity of Raman radiation is calculated by Eq. 3.5-9, taking into account the absorption coefficient a cm ) of water (Fig. 3.5-3) and a constant Raman scattering coefficient (assumed to be equal to 1 cm ). The elastic scattering coefficients as parameters, r = 0, 10, 100, 500 cm , describe the properties of a liquid, a coarse, a medium, and a fine powder, respectively. The traces show the relative output voltage of a Germanium detector. 

The AS value was determined on the assumption that the Raman scattering coefficients Sgauchc and 5 tran.s are independent of the temperature. 

Analytic infrared intensities and Raman scattering coefficients for ethylene molecule from RHF/6-311++G(3d,3p) calculations ... 

Mode Vibrational frequencies (cm-1) Infrared intensities (km/mol) Raman scattering coefficients (A4/a.m.u.) ... 

Optical absorption measurements give band-gap data for cubic sihcon carbide as 2.2 eV and for the a-form as 2.86 eV at 300 K (55). In the region of low absorption coefficients, optical transitions are indirect whereas direct transitions predominate for quantum energies above 6 eV. The electron affinity is about 4 eV. The electronic bonding in sihcon carbide is considered to be predominantiy covalent in nature, but with some ionic character (55). In a Raman scattering study of vahey-orbit transitions in 6H-sihcon carbide, three electron transitions were observed, one for each of the inequivalent nitrogen donor sites in the sihcon carbide lattice (56). The donor ionization energy for the three sites had values of 0.105, 0.140, and 0.143 eV (57). 

The present study demonstrates that the analytic calculation of hyperpolarizability dispersion coefficients provides an efficient alternative to the pointwise calculation of dispersion curves. The dispersion coefficients provide additional insight into non-linear optical properties and are transferable between the various optical processes, also to processes not investigated here as for example the ac-Kerr effect or coherent anti-Stokes Raman scattering (CARS), which depend on two independent laser frequencies and would be expensive to study with calculations ex-plictly frequency-dependent calculations. 

Sample variability is a critical issue in prospective application. For optical technologies, variations in tissue optical properties such as absorption and scattering coefficients can create distortions in measured spectra. This section provides a brief overview of techniques to correct turbidity-induced spectral and intensity distortions in fluorescence and Raman spectroscopy, respectively. In particular, photon migration... 

The optical apparatus used in this work was described in section 8.6 and has the capability of providing both Raman scattering and birefringence measurements simultaneously. The Fourier expansion of the overall Raman scattering signal is given by equation (8.51), and the coefficients are given by equations (8.52) to (8.54). In these expression, a simple, uniaxial form for the Raman tensor was assumed. From these coefficients, the anisotropies in the second and fourth moments of the orientation distribution can be solved as... 

In the case of anti-Stokes Raman scattering with the electric vector of the exciting radiation oriented perpendicularly to the plane of observation, the scattering coefficient is ... 

These coefficients have the dimension of reciprocal length (Mills, 1988), in this context, cm Kubelka and Munk (1931) described the optical properties of pigments by employing the parameters a and r. The Kubelka-Munk theory is the basis of diffuse reflection spectroscopy (Sec. 6.4). We have extended the Kubelka-Munk approach in order to describe the Raman scattering of crystal powders (Schrader and Bergmann, 1967). The results can also be applied to liquids and transparent solids. The procedure is as follows ... 

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