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Raman Bands (raman + bands)
Selected AbstractsMicro-Raman spectroscopy of decorated pottery from the Iberian archaeological site of Puente Tablas (Jaén, Spain, 7th,4th century B.C.)JOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2010D. Parras Abstract In this paper, Raman spectroscopy is used for the first time to identify the pigments on decorated antique Iberian pottery. Ceramic fragments of type Real and others from the archaeological excavation in the oppidum Puente Tablas were examined. Different types of iron oxide pigments (hematite and goethite) were identified, along with amorphous carbon. In some samples, the presence of chalk or gypsum could be demonstrated. Some unattributed Raman bands are believed to be associated either with post-burial organic deposition or with silicate materials that are present in red ochre. It was possible to relate the findings with geological data from the region and to make assumptions on a local production. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of the uranyl mineral pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2OJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Ray L. Frost Abstract Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (SO4)2, units and of water molecules. The published formula of pseudojohannite is Cu6.5(UO2)8[O8](OH)5[(SO4)4]·25H2O. Raman bands at 805 and 810 cm,1 are assigned to (UO2)2+ stretching modes. The Raman bands at 1017 and 1100 cm,1 are assigned to the (SO4)2, symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm,1 are assigned to the (SO4)2,,2 bending modes. The bands at 210 and 279 cm,1 are assigned to the doubly degenerate ,2 bending vibration of the (UO2)2+ units. UO bond lengths in uranyl and OH···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd. [source] Nanocarbon materials: probing the curvature and topology effects using phonon spectraJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Sanju Gupta Abstract Much has been learned from the use of resonance Raman spectroscopy and high-resolution transmission electron microscopy techniques about the micro-/nanoscopic structure of various nanostructured carbons. However, they still possess some features that are not entirely understood particularly in terms of topological characteristics, which go beyond making a distinction with just the geometrical structure at nanoscale. To effectively utilize the potential of these materials for technological needs, understanding both the geometrical and topological structure and perhaps relating these attributes to physical (optical/electronic, lattice vibrational) properties become indispensable. Here, we make an attempt to describe the differences between various nanostructures and provide geometrical and topological property assessment semiquantitatively by monitoring the phonon spectra using resonance Raman spectroscopy thereby also capturing the electronic spectra. We elucidate the notion of global topology and curvature for a range of technologically important nanoscale carbons including tubular (single-, double- and multiwalled nanotubes, peapod), spherical (hypo- and hyperfullerenes, onion-like carbon) and complex (nanocones, nanohorns, nanodisks and nanorings) geometries. To demonstrate the proof-of-concept, we determined the variation in the prominent Raman bands of the respective materials, represented as D, G and D* (the overtone of D) bands, as a possible topological or curvature trend due to their sensitivity toward structural modification. The latter arises from local topological defects such as pentagons giving rise to curved nanocarbons. In this study, we provide systematics of their variation with respect to their geometric forms and compare with highly oriented pyrolytic graphite and monolayer graphene since the nanocarbons discussed are their derivatives. Once established, this knowledge will provide a powerful machinery to understand newer nanocarbons and indeed point to an unprecedented emergent paradigm of global topology/curvature , property , functionality relationship. We emphasize that these concepts are applicable to other topologically distinct nanomaterials, which include boron-nitride (BN) nanotubes and nanotori, helical gold nanotubes and Möbius conjugated organics. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of the magnesium-carbonate minerals,artinite and dypingiteJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009Ray L. Frost Abstract Magnesium minerals are important in the understanding of the concept of geosequestration. The two hydrated hydroxy magnesium-carbonate minerals artinite and dypingite were studied by Raman spectroscopy. Intense bands are observed at 1092 cm,1 for artinite and at 1120 cm,1 for dypingite, attributed ,1 symmetric stretching mode of CO32,. The ,3 antisymmetric stretching vibrations of CO32, are extremely weak and are observed at 1412 and 1465 cm,1 for artinite and at 1366, 1447 and 1524 cm,1 for dypingite. Very weak Raman bands at 790 cm,1 for artinite and 800 cm,1 for dypingite are assigned to the CO32,,2 out-of-plane bend. The Raman band at 700 cm,1 of artinite and at 725 and 760 cm,1 of dypingite are ascribed to CO32,,2 in-plane bending mode. The Raman spectrum of artinite in the OH stretching region is characterised by two sets of bands: (1) an intense band at 3593 cm,1 assigned to the MgOH stretching vibrations and (2) the broad profile of overlapping bands at 3030 and 3229 cm,1 attributed to water stretching vibrations. X-ray diffraction studies show that the minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality, and explains why the Raman spectra of these minerals have not been previously or sufficiently described. Copyright © 2008 John Wiley & Sons, Ltd. [source] Thermo-Raman spectroscopy of synthetic nesquehonite , implication for the geosequestration of greenhouse gasesJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2008Matthew C. Hales Abstract Pure nesquehonite (MgCO3·3H2O)/Mg(HCO3)(OH)·2H2O was synthesised and characterised by a combination of thermo-Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo-Raman spectroscopy shows an intense band at 1098 cm,1, which shifts to 1105 cm,1 at 450 °C, assigned to the ,1CO32, symmetric stretching mode. Two bands at 1419 and 1509 cm,1 assigned to the ,3 antisymmetric stretching mode shift to 1434 and 1504 cm,1 at 175 °C. Two new peaks at 1385 and 1405 cm,1 observed at temperatures higher than 175 °C are assigned to the antisymmetric stretching modes of the (HCO3), units. Throughout all the thermo-Raman spectra, a band at 3550 cm,1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm,1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175 °C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo-Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO3)·2H2O. Copyright © 2008 John Wiley & Sons, Ltd. [source] Raman and infrared spectroscopic study of the molybdate-containing uranyl mineral calcurmoliteJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008Ray L. Frost Abstract Raman and infrared spectra of calcurmolite were recorded and interpreted from the uranium and molybdenum polyhedra, water molecules and hydroxyls point of view. UO bond lengths in uranyl and MoO bond lengths in MoO6 octahedra were calculated and OH,O bond lengths were inferred from the spectra. The mineral calcurmolite is characterised by bands assigned to the vibrations of the UO2 units. These units provide intense Raman bands at 930, 900 and 868 and 823 cm,1. These bands are attributed to the anti-symmetric and symmetric stretching modes of the UO2 units, respectively. Raman bands at 794, 700, 644, 378 and 354 cm,1 are attributed to vibrations of the MoO4 units. The bands at 693 and 668 cm,1 are assigned to the anti-symmetric and symmetric Ag modes of the terminal MO2 units. Similar bands are observed at 797 and 773 cm,1 for koechlinite and 798 and 775 cm,1 for lindgrenite. It is probable that some of the bands in the low wavenumber region are attributable to the bending modes of MO2 units. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis of hafnium tungstate by a CO2 laser and its microstructure and Raman spectroscopic studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008E. J. Liang Abstract Densely packed hafnium tungstate blocks were synthesized by rapid solidification with a CO2 laser. It is shown that the optimum synthesis conditions for HfW2O8 are around 700 W laser power and 1 mm/s scan speed. Scanning electron microscopy (SEM) observation shows that the blocks consist of oriented nano-threads/rods that grew horizontally on the surface region and vertically in the interior. The orientations of the nanostructures are governed by the heat transfer directions on the surface and in the interior. Raman spectroscopic and X-ray diffraction studies show that the samples solidified in the cubic structure with minor contents of the orthorhombic phase. This is explained by a compressive stress induced during the rapid solidification process due to a sudden drop of temperature of the molten pool to the ambient. The stress is estimated to be about 0.6 GPa by comparison with high-pressure Raman study. Some specific Raman bands appear in the samples synthesized with the laser synthetic route but not in the sample by solid-state reaction. Copyright © 2008 John Wiley & Sons, Ltd. [source] Pressure effects on inter- and intramolecular vibrations in hydrogen-bonded L -ascorbic acid crystalJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2008Hiroko Shimada Abstract Pressure effects on the Raman spectra due to the inter- and intramolecular vibrations of the L -ascorbic acid crystal were studied. The intensity of the Raman bands due to the intermolecular vibrations varies in three different ways by application of pressure. The bands of the first group become stronger, those of the second one become weaker and the third group shows no prominent change in their intensity with increasing pressure. The bands due to the intermolecular vibrations show a blue shift, while the bands due to the intramolecular vibrations shift to the blue or red depending on the vibrational modes by application of pressure. The bands assigned to the OH stretching vibrations shift to the red, the bands assigned to the CO and CC stretching vibrations shift a little to the red and the bands assigned to the other vibrations shift to the blue under high pressure. The following conclusions were derived. (1) The hydrogen bonds forming helixes become stronger and the isolated hydrogen bond becomes weaker with increasing pressure. (2) The bands of the first group owing to the intermolecular vibrations are ascribed to the vibrations related to the helix hydrogen bonds and the second group bands to the isolated hydrogen bond. (3) The CO stretching vibration couples with the CC stretching vibration. (4) The phase transitions take place at 1.8 and 4 GPa in the crystal. Copyright © 2007 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of serum albumins: an effect of proton- and ,-irradiationJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2007Alla Synytsya Abstract Raman spectroscopy was applied to analyse structural changes in serum albumins (bovine serum albumin, BSA; human serum albumin, HSA) following proton and ,-irradiation (0.5, 5 and 50 Gy). Characteristic Raman bands of both polypeptide backbone and amino acid residues were sensitive to irradiation. Significant damage of HSA/BSA was observed only at the highest dose (50 Gy). Raman spectra confirmed radiation-induced denaturation, destruction of helical structures and aggregation of serum albumins. The differences in the dose-dependent effects of proton and ,-radiation on studied proteins are discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Some aspects of SERS temporal fluctuations: analysis of the most intense spectra of hydrogenated amorphous carbon deposited on silverJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2007Andrzej Kudelski Abstract Surface-enhanced Raman scattering (SERS) spectra of hydrogenated amorphous carbon (aC:H) deposited on silver substrates have been recorded with a confocal Raman microscope. When scattered radiation is collected during a short time from an area of a few square micrometres, the subsequently measured SERS spectra often exhibit strong temporal changes (fluctuations). In this paper we present examples of spectra for which the intensity maxima of the fluctuating narrow Raman bands are significantly higher than that of the background (the background is usually dominated by two broad Raman bands centred at about 1350 and 1590 cm,1). In a series of successively measured spectra, one can find spectra with noticeably different total integral intensity. This suggests that the results of averaging the spectra revealing strong and weak fluctuations may be different (at least in intensity). The influence of some electrolytes on the SERS spectral fluctuations is also analysed. Our experiments revealed that the efficiencies of quenching of the SERS spectral fluctuations by various electrolytes are significantly different. We suggest that only anions directly interacting with the metal surface quench strong SERS fluctuations, and that the large differences between chloride and perchloride solutions are caused by differences in the strength of interaction of Cl, and ClO4, anions with the silver surface. Copyright © 2007 John Wiley & Sons, Ltd. [source] Multianalyte immunoassay based on surface-enhanced Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2007Yan Cui Abstract In this paper, two immunoassay methods based on SERS are developed for multiplex analysis, both of which stemmed from the concept of forming a sandwich structure ,capture antibody substrate/antigen/Raman-reporter-labeled immuno-nanoparticles'. They are two-molecule labeled one-nanoparticle and one-molecule labeled two-nanoparticle methods. In both the methods, two different antibodies covalently bound to a solid substrate can specifically capture two different antigens from a sample. The captured antigens in turn bind selectively to their corresponding antibodies immobilized on Raman-reporter-labeled nanoparticles. Multianalyte immunoassay is successfully demonstrated by the detection of characteristic Raman bands of the probe molecules only when the antigen and antibody are matched. Copyright © 2007 John Wiley & Sons, Ltd. [source] Raman spectroscopy of the borosilicate mineral ferroaxiniteJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2007Ray L. Frost Abstract Raman spectroscopy, complemented by infrared spectroscopy, has been used to characterise the ferroaxinite minerals of the theoretical formula Ca2Fe2+Al2BSi4O15(OH), a ferrous aluminium borosilicate. The Raman spectra are complex but are subdivided into sections on the basis of the vibrating units. The Raman spectra are interpreted in terms of the addition of borate and silicate spectra. Three characteristic bands of ferroaxinite are observed at 1082, 1056 and 1025 cm,1 and are attributed to BO4 stretching vibrations. Bands at 1003, 991, 980 and 963 cm,1 are assigned to SiO4 stretching vibrations. Bands are found in these positions for each of the ferroaxinites studied. No Raman bands were found above 1100 cm,1 showing that ferroaxinites contain only tetrahedral boron. The hydroxyl stretching region of ferroaxinites is characterised by a single Raman band between 3368 and 3376 cm,1, the position of which is sample-dependent. Bands for ferroaxinite at 678, 643, 618, 609, 588, 572, 546 cm,1 may be attributed to the ,4 bending modes and the three bands at 484, 444 and 428 cm,1 may be attributed to the ,2 bending modes of the (SiO4)2,. Copyright © 2006 John Wiley & Sons, Ltd. [source] Raman spectra indicative of unusual water structure in crystals formed from a room-temperature ionic liquidJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2006Hiroko Miki Abstract Formation of crystals with unusual water structure has been found to take place in an ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate (bmim[FeCl4]). The Raman spectrum of a crystal formed in bmim[FeCl4] showed two prominent Raman bands ascribed to H2O. Another crystal formed in bmim[FeCl4] exposed to D2O atmosphere showed Raman bands of H2O, HOD and D2O. These findings indicate that an unusually high concentration of water is contained in the crystals. The observed Raman bands of the HOH, HOD and DOD bending modes are unusually narrow, implying an unknown unique structure of water. Copyright © 2006 John Wiley & Sons, Ltd. [source] Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3-trifluoropropyl- silane and 3,3,3-trifluoropropylsilane- d3,JOURNAL OF RAMAN SPECTROSCOPY, Issue 1-3 2006Peter Klaeboe Abstract Infrared spectra of 3,3,3-trifluoropropylsilane (CF3CH2CH2SiH3) and 3,3,3-trifluoropropylsilane- d3 (CF3 CH2CH2SiD3) were obtained in the vapour, liquid, and crystalline solid phases in the range 4000,50 cm,1. Additional spectra in argon matrices at 5 K were recorded before and after annealing to temperatures 20,34 K. Raman spectra of the compounds as liquids were recorded at various temperatures between 296 and 183 K and spectra of the amorphous and crystalline solids were obtained. The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the two vapours were shock-frozen on a cold finger at 78 K, they turned partly crystalline immediately. After subsequent annealing to 140,150 K, ca 7,9 Raman bands of both molecules present in the liquids vanished in the crystal. Similar variations in intensity were observed in the corresponding infrared spectra before and after annealing. The spectra revealed the existence of one conformer (anti) in the crystal. From Raman intensity variations of three independent pairs of anti and gauche bands between 298 and 173 K for the parent compound, and 298 and 183 K for the deuterated analogue, the values ,confHo(gauche,anti) = 4.1 ± 0.3 kJ mol,1 for the parent compound and the same value for the deuterated species were obtained in the liquid state. Annealing experiments in the matrices show that the gauche bands vanish after annealing, demonstrating that the anti conformer also has the lower energy here and that the barrier to gauche , anti inter-conversion is around 5,6 kJ mol,1. The spectra of both conformers have been interpreted in detail. Ab initio and DFT calculations at the HF/6,311G**, B3LYP/6,311 G** and MP2/6,311 G** levels gave optimized geometries, infrared and Raman intensities and vibrational wavenumbers for the anti and gauche conformers. The conformational enthalpy difference derived from the calculations was between 6.0 and 4.1 kJ mol,1 with anti being the low energy conformer. Copyright © 2006 John Wiley & Sons, Ltd. [source] Analysis of segregation process of n -alkanes in binary mixtures by FTIR and Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2005Andrzej Hacura Abstract In the FTIR and Raman spectroscopic studies, the phenomena of normal n -alkanes segregation in the binary mixtures of solid-state paraffin at room temperature were examined. Samples, in which one of the ingredients had been deuterated were prepared in different molar concentrations. Components of the mixture separated in time, creating separate domains, were observed in the changing of shape of infrared and Raman bands. The process of segregation depended on the difference of the chains' length of the mixture's ingredients and the molar fraction, in which the mixtures were prepared. The size of the created microdomains has been estimated based on the model describing shape and the splitting of the IR bands developed by Hiebert and Hornig. By applying the micro-Raman imaging technique, a number of surface maps have been obtained indicating the separating process of ingredients of the mixtures. This allowed comparing and verifying time dependent results of the IR study. Copyright © 2005 John Wiley & Sons, Ltd. [source] Raman spectroscopic signature of life in a living yeast cellJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2004Yu-San Huang Abstract We have discovered a Raman spectroscopic signature that sharply reflects the metabolic activity of a mitochondrion in a living yeast cell. Raman mapping experiments on a GFP-labeled yeast cell showed that this signature originated exclusively from mitochondria. Addition of KCN caused a rapid decrease and subsequent disappearance of the signature followed by gradual changes of the phospholipid Raman bands, indicating that respiration was first inhibited by KCN and then lowered metabolic activity gradually deteriorated the double-membrane structure of a mitochondrion. We can now monitor the life and death of a single cell by time- and space-resolved Raman spectroscopy. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effect of pressure and temperature on Raman spectra of solids: anharmonicity,JOURNAL OF RAMAN SPECTROSCOPY, Issue 7-8 2003Guy Lucazeau Abstract This paper gives a brief review of the effect of temperature and pressure on Raman spectra. Anharmonicity, defined by the cubic, quartic and higher terms in the potential expansion, is shown to be responsible for various properties such as dilatation or for variations of wavenumber and half-width of Raman bands with temperature and pressure, or may be strongly involved in phase transitions. This contribution does not pretend to be an exhaustive review on the subject but aims to introduce some basic concepts in a tutorial way before showing how intricated are these manifestations of anharmonicity. Copyright © 2003 John Wiley & Sons, Ltd. [source] Pressure- and temperature-dependent Raman studies of KNbW2O9 hexagonal tungsten bronzeJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2003czka Abstract Pressure- and temperature-dependent Raman studies were performed on KNbW2O9 ferroelectric hexagonal tungsten bronze single crystal. The results suggest that some structural changes, possibly phase transitions, connected with tilting of the WO6 octahedra occur in this material at around 290,350 K and 1.0,1.4 GPa. No changes in the spectra could be observed at the 523 and 543,553 K phase transitions. The data indicate that these phase transitions lead to only weak changes in the vibrational properties of KNbW2O9, which were not observed owing to the large bandwidth of the Raman bands. The Raman studies suggest, therefore, that the structure of the unknown phase, existing below 553 K, differs slightly form the orthorhombic structure present above 553 K. The pressure-dependent study revealed that the 52 cm,1 band, assigned to external vibrations of the WO6 octahedron, consists at ambient temperature and pressure of two overlapping bands. These bands become well separated at high pressure. Copyright © 2003 John Wiley & Sons, Ltd. [source] Raman microspectroscopic study on low-pH-induced DNA structural transitions in the presence of magnesium ionsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2002C. M. Muntean Low-pH-induced DNA structural changes were investigated in the pH range 6.8,2.10 by Raman microspectroscopy. Measurements were carried out on calf thymus DNA in the presence of low concentrations of Mg2+ ions. Vibrational spectra are presented in the wavenumber region 500,1650 cm,1. Large changes in the Raman spectra of calf-thymus DNA were observed on lowering the pH value. These are due to protonation and unstacking of the DNA bases during DNA melting and also to changes in the DNA backbone conformation. The intensities of the Raman bands of guanine (681 cm,1), adenine (728 cm,1), thymine (752 cm,1) and cytosine (785 cm,1), typical of the C2,- endo - anti conformation of B-DNA, are discussed. The B-form marker near 835 cm,1 and the base vibrations in the higher wavenumber region (1200,1680 cm,1) are analysed. Effects of low pH value upon the protonation mechanism of opening AT and changing the protonation of GC base pairs in DNA are discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source] Assignments and hydrogen bond sensitivities of UV resonance Raman bands of the C8-deuterated guanine ringJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2002Akira Toyama Isotope-edited Raman spectroscopy, a combination of site-selective isotopic labeling and Raman difference spectroscopy, is a useful method for studying the structure and interaction of individual nucleic acid residues in oligonucleotides. To obtain basic data for applying isotope-edited Raman spectroscopy to guanine residues, we studied the vibrational modes of UV resonance Raman bands of the C8-deuterated guanine ring by examining the wavenumber shifts upon seven isotopic substitutions (2- 13C, 2- 15N, 6- 18O, 7- 15N, 8- 13C, 9- 15N and 1,- 13C). The hydrogen bond sensitivities of the Raman bands were also investigated by comparing the Raman spectra recorded in several solvents of different hydrogen bonding properties. Some of the Raman bands were found to be markers of hydrogen bonding at specific donor or acceptor sites on the guanine ring. The Raman bands, which shift on C8-deuteration, remain in the difference spectrum between the unlabeled and C8-deuterated guanine rings. Among them, a negative peak around 1525 cm,1 and a strong positive/negative peak pair around 1485/1465 cm,1 serve as markers of hydrogen bonding at N7 and C6O, respectively. Another weak positive/negative peak pair around 1025/1040 cm,1 is sensitive to hydrogen bonding at the proton donor sites (N1,H and N2,H2). The applicability of the hydrogen bond markers has been tested by using a 22-mer oligonucleotide duplex containing eight guanine residues and its analog in which a single guanine residue is C8-deuterated. The difference spectrum shows that the hydrogen bonding state of the guanine residue at the labeled position is consistent with the Watson,Crick base pair structure of DNA. Isotope-edited Raman spectroscopy is a useful tool for studying the hydrogen bonding state of selected guanine residues in oligonucleotides. Copyright © 2002 John Wiley & Sons, Ltd. [source] In situ micro Raman investigation of electrochemically formed halide and pseudohalide films on mercury electrodes,JOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2002Alexandre G. Brolo Oxidation of pure mercury electrodes was followed by in situ surface-unenhanced Raman spectroscopy. A special spectroelectrochemical cell allowed the observation of spectral features of the oxidation products using a Raman microprobe. The electrochemical behaviour of mercury in basic solution, halide (F,, Cl,, Br, and I,) and pseudohalide (SCN,) media was investigated. Insoluble films were formed during the anodic processes in all these systems. The identities of the electrochemically generated films were clearly determined from the Raman spectra. The main product of the electrochemical oxidation of mercury in basic solutions was solid HgO. The anodic behaviour of mercury in the presence of halide yielded insoluble Hg2X2 compounds (where X is the halide). The time dependence of the Raman signals indicated a diffusion-controlled growth of the halide films. The oxidation of mercury in SCN, solutions also produced a solid precipitate [Hg2(SCN)2]. Raman bands due to soluble mercury(II) thiocyanate complexes [Hg(SCN)x2,x], present in the electrochemical diffusion layer, were also observed. Copyright © 2002 John Wiley & Sons, Ltd. [source] Fourier transform Raman spectroscopic study of pressure-induced ligand bond activation in a molybdenum,sulfur cluster,JOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2002Ian S. Butler Fourier transform Raman spectra of the prototype, triangular, transition metal,sulfur cluster anion [Mo3(S2)6S]2, were recorded at pressures up to 60 kbar with the aid of a diamond-anvil cell (DAC). The pressure dependences (,,/,p) of the Raman bands indicate a structural change at around 10,15 kbar. The SS stretching mode for the bridging disulfide ligands exhibits a slightly negative ,,/,p value (,0.08), suggesting that SS bonds are weakened, i.e. activated, at high pressures. This pressure-induced activity parallels the observed nucleophilic substitution reactivity of the S2 groups in this molybdenum cluster anion. In view of this, a preliminary investigation of the reaction between [Mo3(S2)6S]2, and CN, was undertaken in the solid state in the DAC under high pressure. Copyright © 2002 John Wiley & Sons, Ltd. [source] Polarized infrared and Raman spectra of KGd(WO4)2 and their interpretation based on normal coordinate analysisJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2002L. Macalik The direction of the transition dipole moments for the vibrations of the single WOW and double WOOW oxygen bridges in layered scheelite tungstates is derived from the Polarized infrared and Raman spectra of the KGd(WO4)2 single crystal. Their experimental values are compared with those obtained from the calculated atomic Cartesian displacements for the particular normal modes. The assignment of the IR and Raman bands to the respective molecular vibrations was obtained on the basis of the normal coordinate analysis and potential energy distribution. Copyright © 2002 John Wiley & Sons, Ltd. [source] Force constant calculation from Raman and IR spectra in the three non-cubic phases of BaCeO3JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2001H. C. Gupta Raman spectroscopic data for BaCeO3 were modeled with the use of a small set of force constants in its three phases (Pnma, Imma and R3c) using experimental IR and Raman data. An IR reflectance spectrum of BaCeO3 in its Pnma phase is provided for the first time. Raman band symmetry assignments in the Pnma phase were re-examined and the assignments of Genet et al. were confirmed. The distribution of the Raman bands of the Pnma phase between the zone center and X point in Imma is provided and band assignments were extended to the Imma and R3c phases. Calculated values for both Raman- and IR-active modes are provided in the three phases. The variations in force constants throughout the phase transitions are briefly discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] SERS-active sites on various copper substratesJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2001C. Siemes The wavenumbers of the Raman bands of ethylene adsorbed on Cu in ultra-high vacuum depend on the surface structure of the copper substrate. Thus it is possible to differentiate between ethylene adsorbed at Cu(110) sites, Cu(111) sites and surface defect sites of unknown configuration. These latter are the ,SERS-active sites.' Only when these sites are annealed does the distance dependence of SERS follow the expectations from the electromagnetic model of SERS. In the presence of the SERS-active sites, also the signal of ethylene at (111) sites shows a ,first layer effect.' Ethylene adsorbed on cold-deposited copper films shows strong infrared absorption at the same wavenumber as the ethylene at SERS-active sites in Raman scattering, irrespective of the Raman,infrared exclusion rule for the free centrosymmetric ethylene molecule. This raises the possibility that SERS-active sites are also infrared-active sites. The SERS-active sites at stepped Cu surfaces decorated by 3 nm of cold-deposited copper anneal below 200 K, whereas they prevail beyond 400 K on Cu island films. Copyright © 2001 John Wiley & Sons, Ltd. [source] Analysis of Phase Coexistence in Fe2O3 -Doped 0.2PZN,0.8PZT Ferroelectric Ceramics by Raman Scattering SpectraJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Man-Kang Zhu In this work, we suggested a method to evaluate quantitatively the effect of doping oxide on the phase coexistence of PbZr1,xTixO3 (PZT)-based ceramics through the analysis of the Raman scattering spectra. Theoretically, the degenerated T3u mode in the cubic phase of PZT will transform as A1(3) and E(4) modes in the tetragonal phase or as rhombohedral (R) modes in the rhombohedral phase below the Curie temperature, which set up the theoretical base to study the phase coexistence in ferroelectric materials. Through separation by fitting of the Raman bands, the shifts and intensities of different Raman vibration modes were determined. A calculation equation representing the phase coexistence was put forward based on the theoretical analysis of the degenerated T3u modes. The results showed that a turning point appears at the Fe2O3 addition of 0.3%. The variation in the electrical properties of the Fe2O3 -doped Pb(Zn1/3Nb2/3)O3 (PZN),PZT ceramics also affirmed the turning point of the phase evolution as the addition of Fe2O3. [source] Large Photoinduced Densification in Organically Modified Germanosilicate GlassesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Jae Hyeok Jang Organically modified germanosilicate (ORMOGSIL) glasses prepared by a sol-gel method showed a large refractive index change on ultraviolet exposure. The large photoinduced refractive index change in the ORMOGSIL glasses is mainly due to the structural densification caused by ultraviolet irradiation. The shifts in frequency of the Raman bands measured at room temperature reveal structural densification by reduction of the average intertetrahedral bonding angle , in the ORMOGSIL glasses. Surface relief patterns by photoinduced densification were directly inscribed on the ORMOGSIL glasses. [source] In situ micro-Raman and X-ray diffraction study of diamonds and petrology of the new ureilite UAE 001 from the United Arab EmiratesMETEORITICS & PLANETARY SCIENCE, Issue 7 2008Dominik C. HEZEL This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine (Fo79.8,81.8) and pyroxene (En73.9,75.2, Fs15.5,16.9, Wo8.8,9.5) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo96.1,96.8. Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro-Raman and in situ synchrotron X-ray diffraction. The main diamond Raman band (LO = TO mode at ,1332 cm,1) is broadened when compared to well-ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm,1. These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 ,m. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock-produced and natural diamonds. [source] Raman scattering analysis of GaN with various dislocation densitiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008T. Kitamura Abstract We characterized GaN crystals with various dislocation densities by micro-Raman spectroscopy. Defects and Strain for the GaN layer were examined through measurements of the Raman shift and the width of the TO phonon bands. The broadening of Raman bands in GaN crystals occurred as the dislocation density increased. The up-shift of the peak frequencies corresponding to compressive strain was observed for the heteroepitaxial samples grown by MOCVD and MBE. The in-plane distribution of defects and strain in epilayers with various dislocation densities was also examined by Raman mapping. The Raman maps showed that the examined phonon frequency and band width in samples fluctuated spatially. The increase of dislocation density in GaN epilayers induced not only the broadening of Raman bands but also increase of fluctuation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural study of NaNO2 embedded into porous glassPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007E. Rysiakiewicz-Pasek Abstract Temperature-dependent Raman study of NaNO2 confined within porous glass with a pore size of 46 nm has been performed. It is demonstrated that the bandwidths and frequencies of the Raman bands as a function of temperature show similar behaviour, but not identical, as those observed for bulk NaNO2. This result indicates that the first-order phase transition mechanism is only slightly modified by embedding NaNO2 into the porous glass. It seems that formation of "premelted state" is not significant in the studied material, at least up to 40-50 K above Tc. At higher temperatures, however, a significant increase of bandwidth of the 1326 cm,1 band is observed, which could indicate appearance of "premelted" state. The dielectric measurements are consistent with this view since they show large increase of dielectric permittivity above 480 K, well below the NaNO2 melting temperature (554 K). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||