Raman spectra of fosterite

The normal modes of the Raman-active phonons in the center of the Brillouin zone in a natural monocrystal of Mg₂SiO₄ were measured by using Raman scattering. All of the modes predicted by group theory were observed and measured. Some deviations from previously published values in synthetic samples were observed for the low energy phonons.     

Intensity convolutions of CARS spectra

A derivation of the convolution integral for finite bandwidth pump and Stokes sources in CARS is given. The resulting “partially coherent” convolution confirms previously published results, and is compared to the widely used incoherent treatment. The effect of intensity convolution choice on multiplex CARS thermometry is evaluated by reducing N₂ data taken in an ethylene-air diffusion flame. N₂ CARS thermometry using multimode pumps is ordinarily not very sensitive to convolution.     

Intensity studies in Raman effect

The dependence of the relative intensities of Raman lines, having different polarisation characters, on the mode of excitation has been studied using unpolarised, horizontally and vertically polarised incident light. Standard intensities have been obtained in the cases of CCl₄, CHCl₃, C₆H₆, C₂Cl₄, C₂H₂Cl₂, C₂H₄Cl₂, C₆H₅Cl, C₆H₅CH₃ and C₆H₅CH₂OH with the intensity of the 458 cm^?1 line of CCl₄ as standard and from these, the values ofα′, the derived polarisability, have been obtained in the case of total symmetric lines characteristic of particular bonds and certain conclusions regarding the intensity variations of corresponding lines in the different liquids have been arrived at. Values of derived anisotropy have also been obtained in the case of the depolarised lines relative to that of 313 cm^?1 line in CCl₄.     

Intensity studies in Raman effect

The intensities of Raman lines due to CH, CH₂ and CH₃ groups in the case of some n-paraffin hydrocarbons have been obtained relative to the peak intensity of the 458 cm^?1 line of CCl₄ and compared. The integrated intensity as well as the standard intensity of the C=O frequency in some unconjugated and conjugated ketones, aldehydes and esters have been obtained and the influence of conjugation has been discussed. The intensity of the C=C frequency has also been obtained in the conjugated compounds and compared with the results obtained for the unconjugated compounds.     

Intensity of a Raman Overtone Band

Placzek [1] was the first to derive general expressions for the intensities of overtones in case of Raman scattering. He assumed electrical anharmonicity. However, he left the expressions for the derivations of the polarizability tensor undetermined. In 1941, a classical and semiempirical theory was developed by Wolkenstein [2]. He assumed the validity of the additivity of bond polarizabilities. However, the expressions derived by him for the intensities of overtones remain yet to be verified. It is the purpose of this paper to derive a formula for Raman polarizability tensor for overtones of (intramolecular) vibrational spectra along the lines of Kondilenko et al. [3,4]     

High-temperature Raman spectra of KDP:Ni crystal

High-temperature Raman scattering measurements of KDP doped with Ni (1% weight) were performed over the spectral range 50–1200 cm^?1. The X-ray powder diffraction patterns taken at room temperature and analyzed by Rietveld refinement showed that doped samples of KDP:Ni have the same tetragonal structure of a pure KDP crystal, but with a contraction of the crystalline cell. The behavior of the high-temperature Raman spectra indicate that two phase transitions occur, one at 413 K and another one at 443 K. These phase transitions occur at temperatures below the thermal dehydratation point, 488 K. DTA and TGA measurements reveals that KDP:Ni and pure KDP have the same thermal dehydratation temperature.     

Fast reconstruction of Raman spectra from narrow‐band measurements based on Wiener estimation

Raman spectroscopy has demonstrated great potential in clinical and biomedical applications. However, slow data acquisition due to weak Raman signals has prevented its wide use, especially in an imaging setup. In this paper, we propose a novel solution in which the full Raman spectrum can be rapidly reconstructed from a few narrow‐band measurements based on Wiener estimation. This method, using both traditional Wiener estimation and modified Wiener estimation, has been evaluated on Raman spectra collected from live, apoptotic and necrotic leukemia cells with several different types of band‐pass filter choices. Two rules of thumb were identified to guide the choice of filters. Our results indicate that the agreement between reconstructed and measured Raman spectra was excellent according to either the mean root mean square error or the classification accuracy. Therefore, Raman reconstruction from narrow‐band measurements represents a new direction in fast Raman imaging for the investigation of fast changing phenomena. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman spectra of amorphous SiC

It has been found that the condition of the sample preparation exerts large influence on the structural disorder of the films. For the sample prepared by sputtering method, the dependence of CC band on substrate temperature T_s and partial pressure of SiH₄ during the sputtering has been measured.     

Raman spectra of carbyne-fullerene structures

Carbon films grown based on sintering of carbon nanoclusters 1–3 nm in size are studied by the Raman scattering (RS) method. A comparison of RS spectra of fullerene, β-carbyne, diamond, and obtained carbon films allowed the assumption that the film structure corresponds to “carbyne-fullerenes” whose existence was theoretically predicted in [14–16].     

Raman spectra of cadmium titanate

Polarized Raman spectra of CdTiO₃ single crystals are recorded for the first time over the frequency range 5 < ν < 1000 cm^?1 at temperatures of 10 to 1200 K. The emphasis was on the low-frequency range, where an anomalous temperature dependence of a few phonon modes was observed. At high temperatures, four phonon modes exhibiting a behavior typical of soft modes were found to exist. These phonon modes are assumed to restore the cubic symmetry of the lattice. Their extrapolated temperature dependences suggest that there exists a sequence of three hypothetical high-temperature phase transitions analogous to those observed in the genuine perovskite CaTiO₃. At temperatures below 78 K, the Raman spectrum exhibits new lines associated with polar distortions of the unit cell. At low frequencies, three lines are observed whose parameters exhibit an anomalous behavior typical of soft modes in a ferroelectric phase. Several different polar states are assumed to exist at low temperatures.     

Raman spectra of alkali halides

In this article, we present a comparative study of the Raman spectra of alkali halides in relation to the lattice dynamics ofBorn andRaman. It is shown that the experimentally observed limit of the second-order spectra in almost all the cases can be explained well by the Lyddane-Sachs-Teller relation. It is also seen, while, an explanation of the second-order Raman spectrum of a crystal of diamond or zinc blende structure requires the frequencies from the critical points,W, Γ, X andL inBorn's analysis, the frequencies fromΓ, X andL alone are sufficient and necessary for an interpretation of the same onRaman's model. Some similarities in the determination of the long wave properties of crystals like elastic constants and limiting frequencies of the lattice vibrations in the symmetry directions in both the models are pointed out.     

近代Raman光谱技术

介绍几种近代拉曼（Raman）光谱技术及其在科学中的应用。     

Raman spectra of silicon monoxide

The stoichiometric thin films of SiO have been studied by Raman scattering. The spectra indicate three main peaks at 444 cm⁻¹, 454 cm⁻¹ and 502 cm⁻¹ which may correspond to an atomic arrangement of tetrahedra of the type SiSi_yO_4−y where y ≠ 0 and y ≠ 1. The results contradict the mixture model (Si+SiO₂) and show that the SiO oxide cannot be considered as a mixture of Si and SiO₂.     

Raman spectra of chainlike organopolysilane

Chainlike methyl-propyl-polysilane, which was stable even in air, has been synthesized to investigate the vibrational properties of long-chained-silicon skeletons. The vibrational frequencies for the LO and TO like modes, in which the silicon skeletons vibrate along and vertically, respectively, to the chain-direction, are definitely split due to the reduction in the crystallographic symmetry. The frequency for the LO like mode is hardly affected by the side chains attached to the back bones for the tetrahedrally bonded silicon skeletons. On the contrary, the frequency is greatly affected by the side chains for the TO like mode, which is due to the mass effect. In the case of the heavy side chains, the frequency for Si-(side chains) anti-symmetry like stretching vibrations becomes lower, and comparable to that for Si—Si vibrations.     

Effects of alcohols on multi-bubble sonoluminescence spectra

Spectra of multi-bubble sonoluminescence (MBSL) were measured in argon-saturated water and ethanol solutions in the concentration range 2-100 mM at the frequencies of 116 kHz and 1.0 MHz. The spectral peaks from OH-radical emission near 310 nm were observed at relatively low ultrasonic power at both frequencies. The sub-peaks at 290 and 340 nm were also observed, which are attributed to OH-radical vibronic transition. The MBSL spectra from ethanol solutions indicated that the quenching of OH-radical emission was more efficient than that of underlying continuous spectrum. The continuous spectrum suggested the decrease in temperature with increasing ethanol concentration. The concentration dependence of spectrum quenching showed no frequency dependence. A new peak was observed at 385 nm only at small ethanol concentrations and at the frequency of 1.0 MHz, which attributed to CH or CN molecule emission.     

Amorphous-like Raman spectra of semiconductor microcrystals

The size dependence of Raman scattering from gas-evaporated Si, Ge and GaP microcrystals, for which a free boundary condition can be assumed, has been investigated. As the microcrystals become sufficiently small (smaller than about 100A), spectra very similar to those of amorphous materials are observed, even though electron microscopy proves that they are crystalline. The amorphous-like Raman signals are believed to come from the surface layers of microcrystals.     

Raman spectra of single-crystal C60

We have analysed the Raman spectra of C₆₀ single crystals between room temperature and 10K and studied the temperature-induced phase transition in this material. The spectra show crystal field splitting of the internal Raman modes but no evidence for a line shift near the phase transition. The photo-induced transformation of the crystals and its implication on the interpretation of the Raman spectra is discussed. In the low temperature phase we observed two lines at 30 cm^–1 and 41 cm^–1 which we assign to the librational modes of the crystal.