Raman spectrum and structure of solid P2Cl4

The Raman spectrum of liquid and solid polycrystalline P₂Cl₄ has been recorded from 30 to 700 cm^–1. The far infrared spectrum of the solid has also been reinvestigated. From these data, it is necessary to reassign the P-P stretch (a _g), the PC1₂ rock (a _u) and the PCl wag (b _u). Three lattice modes were observed in the Raman spectrum whereas none was found in the infrared spectrum. No correlation field splitting was observed for any of the intramolecular fundamentals. Although the vibrational data for the crystalline state is best interpreted in terms of atrans (C _2h, 2/_m) conformation, there is some evidence that another form may be present, in small amounts, in the fluid states. Furthermore, no evidence for the torsional mode, previously assigned at 91 cm^–1, has been found and calculations have been made which indicate that such a frequency would lead to an un-acceptably high barrier to internal rotation of the asymmetric PC1₂ rotor.Taken from the thesis of J. E. Saunders which has been submitted in partial fulfillment of the Ph.D. degree.     

Structure refinement and Raman spectrum of silver azide

Silver nitrate reacts with sodium azide to give white powdery silver azide, which can be crystallized in aqueous ammonia. The compound belongs to orthorhombic space group Ibam with a = 5.600(1), b = 5.980(6), c = 5.998(1) Å, and Z = 4. The layer-type structure is constructed from edge-sharing regular rectangles, each composed of silver atoms at its vertices with an enclosed azide anion in a tilted orientation. The linear and asymmetrical structure of the azide anion in crystalline silver azide has been confirmed by its Raman spectrum.     

Raman spectrum of vitreous As2S3

The spontaneous Stokes and anti-Stokes Raman spectrum of vitreous As₂S₃ is reported. The spectrum was recorded with both HeNe and Ar ion laser excitation lines in the transmission and reflection modes respectively. Spectra were recorded at various temperatures between 20°K and 465°K, the softening temperature of As₂S₃ glass. It is shown conclusively that the quasicontinous scattering observed at low wave number shifts (< 100 cm⁻¹) is real in agreement with the theory of Shuker and Gammon and not an arbitrary background as previously reported. An approximate density of vibrational states is deduced from the polarized Raman spectra.     

Computational and Raman studies of phospho-tellurite glasses as ultrabroad Raman gain media

Molecular orbital calculations of two phospho-tellurite model clusters were performed to clarify the origins of the Raman bands in the Stokes region of over 1000 cm^− 1 in phospho-tellurite glasses. The Raman bands could be attributed to two components of 900-1050 cm^− 1 of symmetrical stretching vibrations of PO₄ units and 1050-1200 cm^− 1 of anti-symmetrical stretching vibrations of PO₄ units. It was also clarified that the top of the valence band of phospho-tellurite glasses consists of the lone pair electrons in a TeO_4 + 1 unit and the bottom of the conduction band of the glass consists of the antibonding hybrids of Te 5p and O 2p orbitals in the equatorial plane of a TeO₄ unit.We have developed new phospho-tellurite glasses which have the Raman gain peak of 30 times as large as silica glass or the Raman gain bandwidth of more than 1200 cm^− 1.     

Surface enhanced Raman scattering in an amorphous matrix for Raman amplification

In order to improve the efficiency of Raman Amplifiers, the Surface Enhanced Raman Scattering (SERS) effect of an amorphous matrix of TiO₂ was studied. First, optimisation of the amorphous layer quality was performed by depositing thin films on glass substrates at different temperatures. Then, thin films of amorphous TiO₂ were deposited on silicon commercial gold SERS substrates (Klarite®) by a dip-coating process. The SERS effect was demonstrated by the great difference of Raman intensities of the amorphous TiO₂ matrix dip-coated on active and inactive parts of Klarite® substrate under 633 nm and 780 nm laser excitations in the tail of the Surface Plasmon Resonance band of gold nanoparticles.     

Raman study of liquid sulfur

The Raman spectra of liquid sulfur up to 300°C were measured and discussed. The spectral features were apparently changed over 160°C and these were explained in terms of the ratio between S₈ rings and sulfur chains. The spectral feature of sulfur chains were discussed.     

Raman Scattering From TMTSF-Salts

Abstract

Experimental results for Raman scattering from TSeF, TMTSF-D12, (TMTSF)₂PF₆ and (TMTSF)₂AsF₆ excited with blue-green laser light at liquid nitrogen temperature are reported. A strong resonance effect for excitation of TMTSF with 4579 Å was observed and an assignment for the a_g modes was obtained by comparison with results from TTF. Methyl group modes were identified at 328 cm^?1, 472 cm^?1 and 916 cm^?1, respectively. Charging the TMTSF molecule resulted in a strong frequency shift of -122 cm^?1 and -76 cm^?1 for the a_gu₂ mode, respectively. A study of the temperature dependence of the scattering from molecular modes between 2 K and 300 K did not reveal any correlation with the phase transitions in the conducting compounds.     

High-temperature Raman Investigations of Arsenic Vapour

Raman spectra of arsenic vapour were measured at temperatures up to 1210 K. The intensity ratio of the vibrational modes was used to determine the partial pressure ratio of As₂ and As₄. The data obtained exhibit discrepancies to existing theoretically predicted values. The reason for these differences is yet unclear.     

Inelastic neutron and low-frequency Raman scattering in a niobium-phosphate glass for Raman gain applications

We present measurements of the vibrational spectrum of a binary niobium-phosphate glass in the THz frequency range using inelastic neutron and Raman scattering. The spectra of these glasses show a low-frequency enhancement of the vibrational density of states (“boson peak”). Using a recently developed theory of vibrational excitations in disordered solids we are able to reconcile the measured neutron and Raman spectra using fluctuating elastic and Pockels constants as a model concept. As the spontaneous Raman susceptibility is a key parameter for Raman amplification our results suggest a significant gain profile for application of niobium-phosphate glasses in Raman amplifiers.     

Phonon spectrum of binary ions

For the first time, an attempt is made to describe the phonon spectrum of binary ions (AB, AA, BB type). The experimental structure factors have been used for the case of the Na---Cs alloy system. The Egelstaff formula for liquid metals has been extended to the case of an alloy system. Interesting results are obtained by varying the concentration and temperature.     

Vibrational spectrum of octahedral structures

The vibrational modes of a thirteen-atomic octahedral unit have been derived in the harmonic approximation. The model would approximate the vibrational motion of octahedral complex anions that exist in crystalline or amorphous solids. Comparison of the results of calculations with some available experimental data indicates that the model could fairly account for the observed spectra.     

Raman scattering in sillenite-type crystals

The Raman spectra of Bi₂₄AlPO₄₀ and Bi₃₈ZnO₅₈ crystals have been studied for the first time. The polarization Raman spectra of Bi₁₂GeO₂₀, Bi₁₂TiO₂₀, Bi₂₄AlPO₄₀, and Bi₃₈ZnO₅₈ crystals are also studied. The lines in the Raman spectra of Bi₁₂TiO₂₀, Bi₂₄AlPO₄₀, and Bi₃₈ZnO₅₈ are identified and compared with the lines of the Bi₁₂GeO₂₀ spectra studied earlier. It is shown that the differences in the Raman spectra of the crystals studied are associated with the specific features of their atomic structures.     

Surface enhanced Raman scattering phenomenon

Surface enhanced Raman scattering and surface enhanced fluorescence phenomena are the result of resonance excitation of localized surface plasmons in nanoparticles of some metals. By appropriate choice of the shape and size of metallic nanoparticles, the kind of adsorbed molecules and the wavelength of the exciting light, it is possible to achieve enhancement of the intensity of Raman scattering equal to 10¹²‐10¹⁴. This means that only some molecules inside the exciting light beam are sufficient to record the Raman spectrum. Electromagnetic and chemical mechanisms of enhancement of Raman scattered light and methods of roughness investigation of surfaces exhibiting this promising phenomenon are described in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Raman Scattering in Langasite-Family Crystals

Crystallography Reports - Raman scattering spectra have been investigated in La3Ga5SiO14 langasite crystals with Cr and Fe impurities and La3Ga5.25Ta0.25Si0.5O14 crystalline solid solution. It is...     

Raman Scattering from Liquid Crystals

Abstract

The use of Raman scattering technique as a tool for studying local order in complex liquid crystal systems is illustrated by three examples, namely the locally anisotropic liquid L-phase, lipid membranes, and PDLC's.     

Raman study of gallium arsenide thin films

The influence of deposition parameters on the structure of the gallium arsenide thin films was investigated by Raman scattering. The study was based on the analysis of the first-order Raman spectra which allows for a differentiation between the amorphous component and crystallites of various sizes. The amorphous and crystalline volume fractions were calculated from the integrated intensities of the deconvoluted peaks. It was demonstrated that a transition occurs from μ-GaAs to a-GaAs for particular plasma conditions and substrate temperature. As a function of the deposition parameters the entire range from mostly microcrystalline to completely amorphous films can be obtained. These properties were consistent with the results obtained on the same samples by transmission high-energy electron diffraction and conventional transmission electron microscopy.     

Raman spectroscopic study of hydrogen-containing vitreous silica

It is shown by Raman spectroscopy that high-temperature hydrogen-impregnated vitreous silica contains, in addition to physically dissolved hydrogen, ≡SiOH and ≡SiH groups. A Raman-scattering peak with a wave-number shift of 3685 cm^?1 is assigned to the OH stretching vibration, a peak with a wave-number shift of 2254 cm^?1 to a SiH stretching vibration and a peak with a wave-number shift of 4135 cm^?1 to the presence of physically dissolved hydrogen. When hydrogen was replaced by deuterium, appropriate shifts of the peaks mentioned were found.     

High-pressure Raman study of 6H-PbI2

High-pressure Raman spectra of two solid phases of 6H-PbI₂ have been investigated under hydrostatic pressure up to 14 kbar at ambient temperature. The results are quite reproducible on different samples, when covering the same pressure cycle. A consistent Raman spectrum is obtained after the sample is compressed at least twice. The effect of hysteresis is reduced after several pressure treatments.     

CdZnTe晶片的Raman光谱研究

利用Raman光谱技术研究了CdZnTe晶片表面处理方法、激光功率及波长变化对CdZnTe晶片的Raman谱线影响.研究表明:CdZnTe晶片分别经过机械抛光、Br-MeOH溶液处理以及Br-MeOH溶液+ KOH/甲醇溶液处理后,由于表面晶格完整性的改变, Raman光谱出现了明显变化.采用514.5 nm、632.8 nm及785 nm激光激发CdZnTe晶片时,晶片的Raman波谱也有所不同,其中用785 nm激光激发样品,荧光发光峰位于100～200 cm~(-1)范围,掩盖了晶片Raman特征峰.在对CdZnTe晶片做Raman测试时,尽可能选择较低功率.