摘要:

AbstractInfrared and single‐crystal Raman spectra (20–5000 cm−1) of (CH3)4NClO4were studied in the temperature range 90–320 K. Low‐temperature vibrational studies at 90 K indicated freezing out of the disorder of the anions with an increased number of

ISSN:0377-0486    

DOI:10.1002/jrs.1250220202

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe pressure dependence of the Raman frequencies of cesium vanadate (CsVO3) was studied using a diamond anvil cell up to 15 GPa. From the abrupt changes in the Raman specta three pressure‐induced phase transitions are inferred at 10, 11.5 and 13 GPa. The first phase transition, at 10 GPa, is subtle but affects the VO bond length. It is believed that this transition is of the same nature as that observed in postassium and rubidium vanadates. The much higher transformation pressure in CsVO3is attributed to the anomalous compressibility of the Cs+ion. The second phase transition involves more drastic changes in the high‐frequency region. This is attributed to the rotations and distortions in the VO4tetrahedra which lower the symmetry of the lattice. In the third phase transition, the appearance of broader Raman peaks and the disappearance of the chain deformation modes suggest a partial disorder in the chain stru

ISSN:0377-0486    

DOI:10.1002/jrs.1250220203

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractLa faisabilité du couplage d'une sonde Raman avec une microsonde de Castaing ou un microscope électronique à transmission a été étudiée dès 1986. Dans ce dernier cas, l'épaisseur d'échantillon est très faible et une série de tests a été effectuée sur un matériau modèle, le polystyrène, afin de déterminer expérimentalement la profondeur de champ, ou résolution axiale, d'un microspectrométre Raman à détection multicanale utilisé dans les conditions d'éclairement de l'échantillon et de collection de la lumière diffusée aussi proches que possible de celles correspondant au systéme Raman implanté dans le microscope électronique. Les résultats obtenus montrent que la résolution axiale observée est de l'ordre de 2 μm et qu'un spectre Raman non résonnant de bonne qualité est encore obtenu pour une épaisseur d'échantillon de 50 nm et une résolution latérale de 0.7 μm soit 2 × 10−14g de matériau analysé. Par des traitements numériques bien connus des signaux, il parait possible d'effec

ISSN:0377-0486    

DOI:10.1002/jrs.1250220204

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractExperimental data for depolarization ratio dispersion (DPD) and resonance excitation profiles (REPs) with high spectral resolution (20 cm−1) are provided for seven Raman fundamentals in the region between 1150 and 1650 cm−1of the haeme spectrum from ferrocytochrome c. They cover the resonant region of theQ‐band and the preresonant region of theB‐band. A self‐consistent analysis of the depolarization ratio dispersion (DPD) and resonance excitation profiles (REPs) of these Raman lines is carried out by explicit consideration of multimode mixing. This is achieved by first formulating the Raman tensor in Loudon's formulation to fifth order for each mode, thus restricting the contribution of the fifth‐order term to the vibration itself and omitting multimode contributions. By fitting this expression to the DPDs and REPs of each Raman mode, one obtains coupling parameters which in the next step are inserted into the fifth‐order term of each mode. Thus one takes account of their contributions to multimode mixing. To account for contributions of lower frequency modes, an effective ‘helping rest mode’ was added to the multimode contributions. This procedure yields satisfactory fits to all data sets. The respective fits to the DPD and REP of the oxidation marker line at 1363 cm−1reproduce also the corresponding REP and DPD in the resonant region of theB‐band reported by Champion and Albrecht with a high degree of accuracy. The vibronic coupling parameters obtained are consistent with the weak coupling limit. Further, they confirm the validity of Gouterman's four‐orbital mode

ISSN:0377-0486    

DOI:10.1002/jrs.1250220205

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe application of Raman spectroscopy to the determination of the aromatic content of gasolines and aviation fuels is reported. Since aromatic components have very high Raman cross‐sections owing to large polarizability changes under laser excitation, bands from these components will dominate specific Raman spectral regions. It is expected, therefore, that Raman scattering will be a particularly useful approach to broadly characterizing the fuel hydrocarbon makeup for aromatic content and the properties of fuels which are influenced by aromatic conten

ISSN:0377-0486    

DOI:10.1002/jrs.1250220206

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe solution chemistry of niobium oxide in alkaline and acidic oxalate solutions was investigated by Raman spectroscopy in order to determine the molecular structures of the various aqueous niobium oxide species. The aqueous potassium niobate species were studied as a function of pH from 14.5 to 0.55. Different types of niobium oxide ionic species such as HxNb6O 19(8−x)−(x = 0–3), Nb12O 3612−and Nb2O5·nH2O exist in aqueous solutions, and both the solution pH and niobium oxide concentration determine the different niobium oxide ionic species. The aqueous niobium oxide ionic species are unstable at pH3.0. This study demonstrates the ability of Raman spectroscopy to determine directly the solution chemistry and molecular structures of niobium oxide species in a

ISSN:0377-0486    

DOI:10.1002/jrs.1250220207

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman scattering (SERS) of sulphur‐containing amino acids and peptides (L‐cysteine,L‐cystine,L‐methionine,L‐methionylglycine and glycyl‐L‐methionine) in silver sol was investigated. The Raman signal was enhanced by a factor of about 105. In the pH range 5–11,L‐cysteine was found to absorb on the silver surface through the sulphur atom and also the carboxylate and amino groups. The changes in the SER spectrum ofL‐cysteine observed on lowering the pH of the sol solution below 5 suggested that the amino group was desorbed from the surface on protonation. The SER spectrum ofL‐cystine was similar to that ofL‐cysteine, indicating cleavage of the SS bond on adsorption on the silver surface.L‐Methionine,L‐methionylglycine and glycyl‐L‐methionine also seemed to adsorb via the sulphur atom and also the carboxylate and amino groups in the pH range 5–9. The SER spectra of these compounds showed no concentration

ISSN:0377-0486    

DOI:10.1002/jrs.1250220208

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman and infrared spectra, including two newly reported Raman frequencies, of the hexachloroferrate anion FeCl 63−are presented. Comparison of the vibrational frequencies of MCl4and MCl6species indicates that the stretching frequencies increase with decrease in the coordination number, whereas the bending frequencies decrease. In addition, frequencies of the Cr–N vibrations of the hexacoordinated CrN6system of the Cr(NH3) 63+cation are also r

ISSN:0377-0486    

DOI:10.1002/jrs.1250220209

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractResonance Raman spectra of the acid–base indicator neutral red and its monoprotonated and diprotonated derivatives, excited in the region of the lowest energy electronic absorption bands, are reported. The bands are assigned to vibrations of the phenazine ring system and the substituents. Measurements of the band intensities have permitted an evaluation of the geometric changes attendant upon excitation to the resonant excited stat

ISSN:0377-0486    

DOI:10.1002/jrs.1250220210

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe bands corresponding to the eight OH stretching vibrations of the sucrose molecule in the crystal were identified using polarized IR and Raman spectra. They were assigned to the individual vibrations on the basis of the dichroic ratio calculations and evaluation of force constants by the Lippincott‐Schroeder model for seven hydrogen‐bonded OH groups. An explanation of the Raman activity of OH vibrations is proposed. A relationship between the anharmonicity of two OH oscillators and the gyrotropy of the crystal is sugges

ISSN:0377-0486    

DOI:10.1002/jrs.1250220211

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY