Raman scattering measurements

This has been applied successfully by Mizushima and Shimanouchi and by Shauffele and Shimanouchi to measure the stiffness of polyethylene along the chain. The application of Raman spectroscopy to polymers has been greatly facilitated by the introduction of laser sources. To measure the elastic modulus of a hydrocarbon chain, one must identify the vibration frequencies of the accordion-like motion of the planar zig-zag chain. In order to do this, it is necessary to examine spectra of a 

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In Raman spectroscopy, one observes a fascinating phenomenon whereby a randomly ordered molecule can give rise to a highly polarized scattered Raman signal The experimental setup for making 90° Raman scattering measurements is shown in Fig. 2.14. 

A schematic of a PL system layout is shown in Figure 5. This optical system is very similar to that required for absorption, reflectance, modulated reflectance, and Raman scattering measurements. Many custom systems are designed to perform several of these techniques, simultaneously or with only small modifications. 

Holden et al. [27] reported the first Raman results on nanotubes produced from a Co-catalyzed carbon arc. Thread-like material removed from the chamber was encapsulated in a Pyrex ampoule in -500 Torr of He gas for Raman scattering measurements. Sharp first-order lines were observed at 1566 and 1592 cm and second-order lines al 2681 and 3180 cm , but only when cobalt was present in the core of the anode. These sharp lines had not been observed previously in... 

The most often used detection method for the optical sensors are based on absorption, luminescence, reflectance, and Raman scattering measurements. The basic theory and instrumentation of most of these... 

Smith, L. L., R. W. Dibble, L. Talbot, R. S. Barlow, and C. D. Carter (1995). Laser Raman scattering measurements of differential molecular diffusion in nonreacting turbulent jets of H2/CO2 mixing with air. Physics of Fluids 7, 1455-1466. 

Taking into account the results of the IR and Raman scattering measurements, we may conclude that not complete restoration of the IR spectra after outgassing of the hydrogenated SWNTs is a result of appearance of structural disorder in SWNTs due to high pressure/high temperature hydrogenation. 

Figure I. Geometry for typical Raman-scattering measurement...

For Raman scattering measurement, a freshly cleaved sample is directly illuminated with the Ar-ion laser, and the resulting spectrum, accumulated during 10 min, is shown in Fig. 23. The band at 1580 cm 1 corresponds to the in-plane C-C breathing mode of the whole graphite lattice, namely the E2g mode. The band at 2730 cm-1 is an overtone of a lower-energy vibration, and... 

Time resolved coherent anti-Stokes Raman spectroscopy of condensed matter has been recently extended to the femtosecond domain allowing direct and detailed studies of the fast relaxation processes of molecular vibrations in liquids. The vibrational phase relaxation (dephasing) is a fundamental physical process of molecular dynamics and has attracted considerable attention. Both experimental and theoretical studies have been performed to understand microscopic processes of vibrational dephasing. Developments in ultrafast coherent spectroscopy enables one now to obtain direct time-domain information on molecular vibrational dynamics. Femtosecond time-resolved coherent anti-Stokes Raman scattering measuring systems have been constructed (see Sec. 3.6.2.2.3) with an overall time resolution of less than 100 fs (10 s). Pioneering work has been per-... 

Vander Meulen and Ressler (1980) measured the near-lR spectra of proteins in aqueous solution and compared them with the spectra of protein films. Brown et al. (1983) reported multiple internal reflectance spectra of hydrated films of carbonmonoxy and oxy forms of hemoglobin. This work was extended by Findsen et al. (1986), who, using resonance Raman scattering, measured the effects of hydration on the equilibrium and dynamic properties of hemoglobin and its carbonmonoxy complex. There was a substantial effect of hydration on the CO vibration, but no significant effect on the vibrational properties of the heme protein. 

In the present paper we describe the results of X-ray and TOF neutron diffracBon and Raman scattering measurements for aqueous sulfuric acid soluBons with extended composIBon range in order to obtain the intermaBon both on the intermolecular hydrogen-bonded stmcture and on the intramolecular stmctural parameters of SO4 unit in the solutions. 

In the present study, an instmment has been established for polarized and depolarized Raman scattering measurement of supercritical fluid along its isotherm to realize the investigations stated above. Preliminary results for supercritical CF3H are given to draw a schematic picture of the dynamics. 

Fig. 1 Pressure-resistant sample cell for Raman scattering measurement of supercritical fluids.

Figure 4 Comparisons of phase transformation pressures between the X-ray diffraction (XRD) and neutron diffraction (ND) studies and the present results by microscopic observations and in-situ Raman scattering measurements for krypton hydrate, nitrogen hydrate, and methane hydrate.

Raman scattering measurements require larger impurity concentrations than ab sorption measurements. 

Hancock, R.D., Schauer, R. R, Lucht, R. R, and Farrow, R. L. "Dual-Rump Coherent Anti-Stokes Raman Scattering Measurements of Nitrogen and Oxygen in a Laminar Jet Diffusion Flame." Applied Optics 36 (1997) 3217. 

Note that the PL spectra reflect the position of the conduction band minima, and hence phonon energies measured in the PL spectra do not coincide with Raman scattering measurements, which show a common set of dispersion curves for the axial direction of all polytypes [25], The energies of the principal phonons observed in the PL spectra of six polytypes are listed in TABLE 1. The optical absorption and mechanism of excitation and recombination in the seven SiC polytypes discussed here were reviewed in [26]. 

As noted earlier, fused silica optical fiber is used for remote NIR measurements. The same type of fiber optic probe can be used for Raman spectroscopy, and enables remote measurement of samples and online process measurements. In situ reaction monitoring by Raman spectroscopy has been used to study catalytic hydrogenation, emulsion polymerization, and reaction mechanisms. Remote sensing of molecules in the atmosphere can be performed by Raman scattering measurements using pulsed lasers. 

The porous silicon (por-Si) samples were prepared by anodizing of the p+-type Si(100) wafers in a HF ethanol mixture. Subsequent carbonization was carried out in N2(1.5 l/min)/C2H2((l 1/min)) flow at 1000 °C for 30 min. Details of the carbonization procedure were described in [3]. Raman scattering measurements... 

Raman scattering measurements showed the presence of amorphous carbon clusters in porous layer after wet oxidation at 800 °C but no carbon-related RS was detected after oxidation at 950 °C. No carbon clusters was detected by RS after dry oxidation even at temperature as low as 650 °C. Only partial oxidation of nanocrystalline silicon was observed after dry oxidation at 800 °C. 

Until the 1970s only j = (where is the second order Legendre polynomial) was accessible experimentally, but a technique is now available for measuring both <7 2> and (where P is the fourth order Legendre polynomial). It involves polarized Raman scattering measurements on aligned samples. Jen et who developed this... 

Kopelman and co-workers [10] also measured as a function of temperature. At low temperatures, all the polymers studied exhibit properties similar to the properties of fractals. As the temperature increases, h decreases, i.e., the d value increases. In some specimens, h 0 as the temperature is raised. This implies that all the effects described by fractional dimensions are associated with disorder [85]. A number of specimens also behave as fractals at room temperature. It is noteworthy that the d values for the polymers studied vary over wide limits, from 0.8 to 1.8. In the case of PMMA, d exactly corresponds to the spectral dimension determined by Raman scattering measurements [22, 35] it is 1.8 in both cases. 

RAMAN SCATTERING MEASUREMENTS ENABLE MOLECULAR CHARACTERIZATION OF SURFACES IN REAL TIME... 

Chehroudi, B., Cohn, R., Talley, D., Badakhshan, A. (2000). Raman scattering measurements in the initial region of sub- and supercritical jets. 36th AIAA/ASME/S AE/ASEE Joint Propulsion Conference and Exhibit, Huntsville, AL. AIAA 2000-3392. 

Angle-resolved depolarized Resonance Raman scattering measured by excitation of pigments within their absorption bands also yield the order parameters and of the pigments in the membranes (5). 

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