Laser-Raman scattering spectroscopy

Raman scattering spectroscopy is used to probe the vibrational excitations of a sample, by measuring the wavelength change of a scattered monochromatic light beam. This is usually performed by impinging a monochromatic laser beam to the sample surface, and by recording the scattered beam spectrum. 

Kitahara, K. Yamazaki, R. Kurosawa, T. Nakajima, K. Moritani, A. 2002. Analysis of stress in laser-crystallized polysilicon thin films by Raman scattering spectroscopy. Jpn. J. Appl. Phys. 41 5055-5059. 

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). 

Y. Ozaki and K. Iriyama, Potential of Raman Spectroscopy in medical science, in Laser Light Scattering Spectroscopy of Biological Objects (J. Stepanek, P. Anzenbacher, and B. Sedlacek, eds.). Elsevier, Amsterdam, 1987. 

Surface-Enhanced Raman spectroscopy (SERS) [10] is also one of the analytical tools for a sample s surface. When laser beams with frequency vq irradiated to the sample, some of the beams are scattered. Almost all of the frequency of the scattered beams is the same as that of incident beam (vq), but the fi equency of some scattered beams (vo Vi) is slightly different fi om that of the incident beam. This is called Raman scattering spectroscopy (RSS). The frequency of lattice vibration of the samples is Vj so that RSS gives us knowledge concerning molecular stmcmre, crystal structure and residual stress. The combination of RSS with an optical microscope as well as an atomic force microscope (AFM) is also effective for spatial distribution analysis. 

Prochazka, M., J. Stepanek, and J. Bok (2003). Ag+ and Ag° coordination of porphyrins adsorbed on laser ablated Ag colloids monitored by surface-enhanced resonance Raman scattering spectroscopy. Main Group Met. Chem. 26, 317. 

Raman Scattering Spectroscopy (Renishaw 2000 system), with an Ar -ion laser (>, = 514.5 nm) in backscattering geometry, was used to investigate structural modifications of samples. The Raman shift was calibrated for the diamond peak at 1332 cm. All measurements were carried out in air at room temperature. 

Ultraviolet laser ablation Ultraviolet laser desorption/ionisation Ultraviolet photolysis Ultraviolet resonance Raman scattering/spectroscopy Video Image Enhanced Evaluation of Weathering Visible... 

Photons Laser optical-emission spectroscopy (LOES) Light (Raman) scattering spectroscopy (LS) Fourier transform infrared spectroscopy (FTIR) Ellipsometry (E) Evanescent wave spectrofluorimetry (EWS) X-ray photoelectron spectroscopy (XPS) Ultraviolet photoelectron spectroscopy (UPS) Photodesorption (PD)... 

Unlike the typical laser source, the zero-point blackbody field is spectrally white , providing all colours, CO2, that seek out all co - CO2 = coj resonances available in a given sample. Thus all possible Raman lines can be seen with a single incident source at tOp Such multiplex capability is now found in the Class II spectroscopies where broadband excitation is obtained either by using modeless lasers, or a femtosecond pulse, which on first principles must be spectrally broad [32]. Another distinction between a coherent laser source and the blackbody radiation is that the zero-point field is spatially isotropic. By perfonuing the simple wavevector algebra for SR, we find that the scattered radiation is isotropic as well. This concept of spatial incoherence will be used to explain a certain stimulated Raman scattering event in a subsequent section. 

In FT-Raman spectroscopy the radiation emerging from the sample contains not only the Raman scattering but also the extremely intense laser radiation used to produce it. If this were allowed to contribute to the interferogram, before Fourier transformation, the corresponding cosine wave would overwhelm those due to the Raman scattering. To avoid this, a sharp cut-off (interference) filter is inserted after the sample cell to remove 1064 nm (and lower wavelength) radiation. 

Special Raman Spectroscopies. The weakness of Raman scattering results typically in the conversion of no more than 10 of the incident laser photons into a usable signal, limiting the sensitivity of conventional spontaneous Raman spectroscopy. This situation can be improved using alternative approaches (8,215,216). 

Because Raman spectroscopy requires one only to guide a laser beam to the sample and extract a scattered beam, the technique is easily adaptable to measurements as a function of temperature and pressure. High temperatures can be achieved by using a small furnace built into the sample compartment. Low temperatures, easily to 78 K (liquid nitrogen) and with some diflSculty to 4.2 K (liquid helium), can be achieved with various commercially available cryostats. Chambers suitable for Raman spectroscopy to pressures of a few hundred MPa can be constructed using sapphire windows for the laser and scattered beams. However, Raman spectroscopy is the characterizadon tool of choice in diamond-anvil high-pressure cells, which produce pressures well in excess of 100 GPa. ... 

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