Showing papers on "Raman spectroscopy published in 1987"
TL;DR: In this article, the infrared and Raman spectra of powder samples of WO3 (monoclinic and hexagonal) and XH 2 O (x = 1,2, 1 3 ) have been recorded and the most characteristic vibrations are discussed with reference to the available structural data.
856 citations
582 citations
TL;DR: In this paper, the Raman microprobe was used to study the vibrational spectra of celluloses and to identify hydrogen motions in deuterated celluloses, which aided in the interpretation of vibrational spectrum of cellulose.
421 citations
TL;DR: In this article, the band-gap energy (Eg) of metalorganic vapor phase epitaxially (MOVPE) grown Ga 0.5In0.5P lattice matched to (001) GaAs is presented as a function of a wide range of V/III ratios and growth temperatures.
Abstract: The band‐gap energy (Eg) of metalorganic vapor phase epitaxially (MOVPE) grown Ga0.5In0.5P lattice matched to (001) GaAs is presented as a function of a wide range of V/III ratios and growth temperatures. Photoluminescence, Raman scattering spectroscopy, transmission electron microscopy, and impurity diffusion were used to investigate this functional relationship. Two pieces of evidence are shown which demonstrate that MOVPE Ga0.5In0.5P epitaxial layers with ‘‘abnormal’’ Eg∼1.85 eV and ‘‘normal’’ Eg∼1.9 eV correspond to an ordered and a random (Ga,In) distribution on column III sublattices, respectively. In an ordered state, a sequence of (110) planes...GaGaInInGaGaInIn...in the [110] direction is the most probable distribution.
363 citations
TL;DR: The fluorescence spectra have been measured from native chromophores in malignant and normal human breast and lung tissues and the spectra profiles were found to be different in both species.
Abstract: The fluorescence spectra have been measured from native chromophores in malignant and normal human breast and lung tissues. The spectra profiles were found to be different in both species. In addition, one normal breast tissue exhibited Raman spectra.
363 citations
TL;DR: The X-ray absorption near-edge spectra (XANES) of the L1 tungsten edge in WO3/Al2O3 samples indicate that the symmetry of the Tungsten environment depends on both the surface coverage and the presence of coordinated water as mentioned in this paper.
Abstract: The X-ray absorption near-edge spectra (XANES) of the L1 tungsten edge in WO3/Al2O3 samples indicate that the symmetry of the tungsten environment depends on both the surface coverage and the presence of coordinated water. At coverages of less than 1/3 monolayer, in the absence of coordinated water, the XANES spectrum indicates a distorted tetrahedral structure for the surface tungsten oxide species. Samples exposed to air at room temperature have water molecules coordinated to the surface tungsten oxide species and produce an octahedral site symmetry, but the water is removed by heating to 500 "C. The Raman spectra of the W03/A1203 samples are consistent with a distorted tetrahedral tungsten oxide environment and, in addition, show features due to W=O and W-0-W bonds. These results suggest that the surface tungsten oxide is present as both isolated and dimeric tetrahedra. At coverages approaching a monolayer, in the absence of coordinated water, a significant fraction of the surface tungsten oxide sites appears to have a distorted octahedral environment in the XANES spectra. At this high coverage the effect of coordinated water molecules is much less evident than at low coverage. The Raman results, however, only provide information about the tetrahedral component because the Raman cross section of the tetrahedral tungsten oxide is much higher than the octahedral tungsten oxide. The Raman spectra show features of W4 and W-0-W bonds in the tetrahedral fraction of the surface tungsten oxide monolayer on alumina. These observations are consistent with a surface complex where the supported tungsten oxide has formed a polymeric structure on the alumina support composed of W04 and W06 units jointed in infinite chains.
273 citations
TL;DR: In this paper, an effective medium approximation model was applied to the optical constants and it was shown that, whatever the ion bombardment rate and energy increased the diamond-like (sp3 carbon) component and decreased the hydrogen content.
243 citations
TL;DR: In this article, a high frequency shift of the main Raman peak is observed with increasing photon energy, interpreted in terms of scattering from π-bonded carbon clusters which is resonantly enhanced for incident photon energies approaching the π−π* resonance.
Abstract: Resonant Raman spectroscopy has been used to study amorphous hydrogenated carbon films. For films containing both sp2 and sp3 bonded carbon a well‐defined high‐frequency shift of the main Raman peak is observed with increasing exciting photon energy. This shift is interpreted in terms of scattering from π‐bonded carbon clusters which is resonantly enhanced for incident photon energies approaching the π–π* resonance.
239 citations
200 citations
TL;DR: In this paper, the surface-enhanced Raman scattering of benzenethiol was investigated in a silver sol and it was found that benzenetiol was chemisorbed dissociatively on the silver surface by rupture of its SH bond and the benzenetsiolate formed on adsorption was bound to silver via its sulphur atom.
Abstract: The surface-enhanced Raman scattering of benzenethiol was investigated in a silver sol. It was found that benzenethiol was chemisorbed dissociatively on the silver surface by rupture of its SH bond and the benzenethiolate formed on adsorption was bound to silver via its sulphur atom. Using the electromagnetic surface selection rule, the orientation of the benzene ring with respect to the surface plane could not be determined conclusively. However, it seemed likely that benzenethiol was adsorbed face-on to the silver surface.
AT&T1
TL;DR: In this paper, an interface-selective probe of molecular vibrations is used to obtain vibrational spectra of molecular monolayers on metal and semiconductor surfaces, which obey electric dipole selection rules: vibrational modes must be both Raman and infrared active to show sum frequency resonances.
TL;DR: In this paper, surface-enhanced Raman (SER) spectra for adsorbed carbon monoxide were obtained from thin films of platinum and palladium electrodeposited on electrochemically roughened gold, and the major vibrational bands on these surfaces were diagnosed from their frequencies as arising from C-O stretching vibrations.
Abstract: Thin (ca. one to three monolayers) films of platinum and palladium electrodeposited on electrochemically roughened gold are observed to yield surface-enhanced Raman (SER) spectra for adsorbed carbon monoxide. The major vibrational band(s) on these surfaces are diagnosed from their frequencies as arising from C-O stretching vibrations, nu/sub CO/ bound to the transition-metal overlayers rather than to residual gold sites. The observed SFR nu/sub CO/ frequencies are closely similar to (within ca. 10 cm/sup -1/ of) those obtained for these systems from potential-difference infrared (PDIR) spectra. The major SERS and PDIR nu/sub CO/ features for the platinum and palladium surfaces appear at 2060-2090 and 1965-1985 cm/sup -1/, respectively, consistent with the presence of terminal and bridging CO on these two electrodes. The infrared as well as electrochemical properties of these systems are closely similar to those for the corresponding polycrystalline bulk electrodes. A difference between the SER- and IR-active adsorbed CO, however, is that the former undergoes electrooxidation on both surfaces at 0.2-0.3 V higher overpotentials than the latter form. Examination of the potential-dependent SERS bands for metal oxide vibrations, nu/sub PtO/, on the platinum surface shows that the electrooxidation potential for the SERS-active adsorbed CO coincides with that for themore » appearance of the nu/sub PtO/ band. Some broader implications to the utilization of SERS for examining transition-metal surfaces are pointed out.« less
TL;DR: In this article, the authors examined the evolution of Raman spectra of SiC fibres through structural and compositional transformations caused by heat treatment, and they showed that the carbon microcrystals play an important role in maintaining the high mechanical strength of the SiC fibre.
Abstract: We have examined the evolution of Raman spectra of SiC fibres through structural and compositional transformations caused by heat treatment. The SiC fibre was made from polycarbosilane. Raman spectra of the SiC fibre indicate that it consists of (i) amorphous or microcrystalline SiC, (ii) carbon microcrystals, and (iii) silicon oxide. The amount of microcrystalline carbon in the fibre increases with heat treatment temperature up to 1400° C, and it decreases abruptly in those fibres heat treated above 1500° C. The tensile strength of the fibre drops virtually to zero after the heat treatment at 1500° C. Carbon microcrystals are precipitated from the Si-C random network with excess carbon, and they are distributed uniformly in the fibre. These carbon particles suppress the growth of SiC crystals. It is shown that the carbon microcrystals play an important role in maintaining the high mechanical strength of the SiC fibre.
TL;DR: A new method of instantaneously measuring three-dimensional velocity profiles and structure in air and oxygen using Raman excitation and laser-induced electronic fluorescence to generate a time-gated image of the moving oxygen molecules is reported.
Abstract: We report the development of a new method of instantaneously measuring three-dimensional velocity profiles and structure in air and oxygen. No seeding of particles, molecules, or atomic species is required. The method combines Raman excitation and laser-induced electronic fluorescence to generate a time-gated image of the moving oxygen molecules.
TL;DR: In this paper, spontaneous Raman scattering has been used to measure the temperature of CH 4 turbulent non-premixed flames using the Rayleigh scattered signal, and the remaining "fluorescence" has been corrected for, using correction curves generated from measurements made in a laminar counterflow CH 4 diffusion flame and a diluted CH 4 N 2 = 1 2 (by vol.) Laminar diffusion flame.
TL;DR: A three-laser, coherent anti-Stokes Raman scattering (CARS) technique for the simultaneous acquisition of spectra from two species has been developed, using a narrow-band, tunable dye-lasers as one of the CARS pump beams.
Abstract: A three-laser, coherent anti-Stokes Raman scattering (CARS) technique for the simultaneous acquisition of spectra from two species has been developed. A narrow-band, tunable dye-laser beam is used as one of the CARS pump beams. The frequency spacing between the spectra of the two species can be adjusted by changing the frequency of the dye-laser pump beam, enabling the spectra to be displayed at high resolution (0.5 cm(-1)) on the same intensified diode array detector.
TL;DR: In this article, laser Raman and Fourier transform infrared spectroscopies as well as X-ray diffraction were used to study the interactions of MoO3 with various metal oxide supports.
TL;DR: In this article, the formation of zeolite Y from colloidal silica and soluble silicate species was investigated by Raman spectroscopy and the role of aging of the reactant mixture was studied.
Abstract: The formation of zeolite Y from colloidal silica and soluble silicate species was investigated by Raman spectroscopy. The role of aging of the reactant mixture was studied. During the nucleation period, the solid amorphous phase consists of predominantly six-membered aluminosilicate rings, which act as building blocks for the formation of zeolite Y. It is essential to have polymeric, highly condensed silicate units as a reactant if zeolite Y crystallization is to take place.
TL;DR: In this article, three basis sets were used: minimum, double-zeta (DZ), and doublezeta plus polarization (dZ+P), and the predicted self-consistent field dissociation energies were 15.1, 19.3, and 14.3 kcal/mol.
Abstract: Ab initio molecular quantum mechanical methods have been used to study the formic acid dimer and several isotopomers. Structures and harmonic vibrational frequencies have been predicted for the monomer, the equilibrium dimer, and the transition state for simultaneous two-hydrogen transfer. In an attempt to systematize results obtained at various levels of theory, three different basis sets were used: minimum, double-zeta (DZ), and double-zeta plus polarization (DZ+P). The predicted self-consistent-field (SCF) dissociation energies D/sub e/ are 15.1 (minimum basis), 19.3 (DZ), and 14.3 (DZ+P) kcal/mol. Further consideration of zero-point vibrational energies and finite temperature effects allows a comparison with several experimental values for ..delta..H/sub 300/. The infrared and Raman intensities (as well as the vibrational frequencies themselves) are compared with available experimental results. Where comparison is possible, the agreement is generally good. An exception occurs for v/sub 18/, the O-D stretch of the (HCOOD)/sub 2/ molecule, where it is concluded that the experimental analysis may be incorrect.
TL;DR: In this paper, the authors derived expressions for the effective phonon deformation potentials of polycrystalline materials, based on the properties of tensor invariants and the Voigt-Reuss-Hill averages.
Abstract: Expressions are derived for the effective phonon deformation potentials of polycrystalline materials, based on the properties of tensor invariants and the Voigt–Reuss–Hill averages [Proc. Phys. Soc. London Sect. A 65, 349 (1952)]. These results, and similar ones for the elastic constants, are used to determine the effect of strains on the long‐wavelength optical phonons exhibited by such materials. Application to polycrystalline Si shows that under a uniaxial or biaxial stress, the triply degenerate phonons split into singlet and doublet components that shift at different rates and appear indistinguishably in the Raman spectrum. The implications of such effects on the Raman band shape are discussed.
TL;DR: In this paper, a line-shape fitting of the coupled modes of the phonon-overdamped plasmon coupled modes in n-type epitaxial films of β-SiC was used to determine the carrier concentrations and damping constants.
Abstract: LO phonon‐overdamped plasmon coupled modes in n‐type epitaxial films of β‐SiC have been measured in the carrier concentration range from 6.9×1016 to 2×1018 cm−3. The carrier concentrations and damping constants are determined by line‐shape fitting of the coupled modes and compared with the values derived from Hall measurements. The concentrations obtained from the two methods agree fairly well. The Faust–Henry coefficient determined from the fitting is 0.35. The line‐shape analysis of the coupled mode has shown that the dominant scattering mechanisms in β‐SiC are deformation‐potential and electro‐optic mechanisms.
TL;DR: In this paper, the effects of experimental parameters on surface-enhanced Raman scattering (SERS) for silver-coated microsphere substrates were investigated and the potential for increasing SERS sensitivity was illustrated by the detection of benzo(a)pyrene, a molecule of environmental and toxicological interest.
Abstract: The effects of experimental parameters on surface-enhanced Raman scattering (SERS) for silver-coated microsphere substrates were investigated. The parameters included sphere size, silver thickness, and excitation wavelength. The SERS signal intensity varied as each of these parameters was changed. The potential for increasing SERS sensitivity was illustrated by the detection of benzo(a)pyrene, a molecule of environmental and toxicological interest, at a concentration well below that possible for normal Raman scattering. This work describes some optimization procedures and demonstrates the possibility for further improving SERS enhancement of these silver-coated microsphere substrates by optimizing experimental parameters.
TL;DR: In this article, the retrogradation kinetics for waxy-corn starch-water and potato starchwater systems were monitored by rapid-scanning, Raman spectroscopy, and the spectra showed that bands in the 480-cm −1 skeletal-mode region and the 2900-cm−1 C-H stretching-mode regions are sensitive to the retro degradation process.
TL;DR: In this paper, the tetrapropylammonium ion is trapped into the amorphous solid phase at the earliest stages of the synthesis in the all-trans configuration.
Abstract: The Raman spectra of the solution and solid phases present during various stages of ZSM-5 synthesis were examined by monitoring the vibrations of the tetrapropylammonium ion. It was found that this cation is trapped into the amorphous solid phase at the earliest stages of the synthesis in the all-trans configuration. Upon crystallization of the zeolite, there is a forced change in the conformation of the trapped tetrapropylammonium cation, such that it can fit into the zig-zag zeolite channels. The Raman spectra of the aluminosilicate zeolite framework is also distinct from other zeolites, such as A, X, and Y, and exhibits a band at 385 cm/sup -1/ characteristic of the five-membered building units of this zeolite.
01 Jan 1987
TL;DR: In this article, the IR and Raman spectra of metalloporphyrins, metallochlorins, and metallophthalocyanines are comprehensively reviewed.
Abstract: Infrared and Raman spectra of metalloporphyrins, metallochlorins, and metallophthalocyanines are comprehensively reviewed The review starts from general explanations of basic properties of resonance Raman (RR) spectra of these compounds Vibrational assignments of IR and RR bands of symmetric metalloporphyrins and their application to asymmetric protoporphyrin IX are interpreted on the basis of the isotopic shift data observed for specifically isotope-labeled porphyrins and of the normal coordinate calculations For iron porphyrins, empirical rules with regard to the relation between the RR spectra and the spin-, oxidation-, and coordination states are explained FeI- and FeIV-porphyrins and porphyrin cation-radical states are also included The internal modes of an axial ligand (L) coordinated to the metal ion (M) as well as the M-L stretching modes and their difference between organic solution and protein matrix are described Based on these data, differences and similarities in the M-L bonds among the three types of metal complexes of the conjugated macrocycles are discussed