Raman scattering geometry

Fig. 4. Raman scattering geometry, viewed along the chain axis of the stretched polymer (Z axis). X is the direction of the incident laser beam, and Y the direction of collection optics.

Figure 10.16 Raman scattering geometry. The laser is incident along the z axis, and the Raman emission is scattered into the volume element dCi = sin Q dO d. ...

Figure 9 Raman-scattering geometries (a) Configuration 1 axis 3 parallel to laser polarization direction, axis 1 along laser propagation direction (b) configuration 2 axis 1 parallel to laser polarization, axis 3 perpendicular to incident propagation direction (c) configuration 3 axis 2 parallel to laser polarization, axis 3 parallel to incident propagation direction.

Usually, particle size has relatively little effect on Raman line shapes unless the particles are extremely small, less than 100 nm. For this reason, high-quality Raman spectra can be obtained from powders and from polycrystalline bulk specimens like ceramics and rocks by simply reflecting the laser beam from the specimen surface. Solid samples can be measured in the 90° scattering geometry by mounting a slab of the solid sample, or a pressed pellet of a powder sample so that the beam reflects from the surface but not into the entrance slit (Figure 3). 

In Raman measurements [57], the 514-nm line of an Ar+ laser, the 325-nm line of a He-Cd laser, and the 244-nm line of an intracavity frequency-doubled Ar+ laser were employed. The incident laser beam was directed onto the sample surface under the back-scattering geometry, and the samples were kept at room temperature. In the 514-nm excitation, the scattered light was collected and dispersed in a SPEX 1403 double monochromator and detected with a photomultiplier. The laser output power was 300 mW. In the 325- and 244-nm excitations, the scattered light was collected with fused silica optics and was analyzed with a UV-enhanced CCD camera, using a Renishaw micro-Raman system 1000 spectrometer modified for use at 325 and 244 nm, respectively. A laser output of 10 mW was used, which resulted in an incident power at the sample of approximately 1.5 mW. The spectral resolution was approximately 2 cm k That no photoalteration of the samples occurred during the UV laser irradiation was ensured by confirming that the visible Raman spectra were unaltered after the UV Raman measurements. 

The electrochemical cell used in our laboratory has been fully described elsewhere (5). The cell body is made of chemically inert Kel-F and the electrode is mounted on a piston so that its surface can be pushed to the optical window, to a spacing of the order of 1-3 microns, in order to minimize the signal from the bulk electrolyte. For Raman scattering spectroscopy the window is of flat fused quartz, and the exciting laser beam is incident at about 60°. The scattered light is collected off-normal, but the geometry is not critical for SERS due to the high sensitivity. Details on the SERS measurements in our laboratory have been reported previously (6,7). 

The metaiioporphyrins form a diverse class of molecules exhibiting complex and varied photochemistries. Until recently time-resolved absorption and fluorescence spectroscopies were the only methods used to study metailoporphyrln excited state relaxation in a submicrosecond regime. In this paper we present the first picosecond time-resolved resonance Raman spectra of excited state metaiioporphyrins outside of a protein matrix. The inherent molecular specificity of resonance Raman scattering provides for a direct probe of bond strengths, geometries, and ligation states of photoexcited metaiioporphyrins. 

Fig. 15 Raman scattering spectra of a STO 16 and b STO 18-23 observed in x(yy)-x scattering geometry (tetragonal notation). Arrows in a indicate positions of DIRS signal and its higher harmonic component [27]...

Fig. 17 Temperature dependencies of the mode observed in ST016 closed circles), STO 18-23 closed squares), and STO 18-32 closed triangles) observed in the scattering geometry x yy)-x. Crosses indicate the results for STO 16 obtained by the hyper-Raman scattering experiment. The corresponding open symbols denotes the half-width at half maximum of the soft u mode spectrum of each specimen [27]...

Fig. 18 Raman scattering spectra of a ST018-23 and b ST018-32 observed in x(yz)-x scattering geometry in a low-temperature region [27]...

Sun, W. X., and Shen, Z. X. 2003. Apertureless near-field scanning Raman microscopy using reflection scattering geometry. Ultmmicroscopy. 94 237 44. 

Fig. 11. Low frequency shift Raman Specfra in the (zy) scattering geometry for various temperatures in FeFj ss)...

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