bluuebunny/crossref_metadata_2025 huggingface dataset:
CARS vibration‐rotation Q‐branch spectrum of hydrogen chloride
Authors: Edwards H. G. M. , Greenhalgh D. A. , Long D. A. , Sherwood G.
Published: May 2005

The self‐broadening of the Q‐branch vibration‐rotational lines in the CARS spectrum of HCl was studied over the pressure range 0.002‐1.000 bar and the temperature range 298‐1048 K. The broadening coefficients, σp, are dependent on J at 298 and 550 K but are independent of J at higher temperatures; the σp value of 1048 K is only about 25% of its value for Jmax at 298 K.
Near‐infrared fiber‐optic sample cell: Applications to fourier transform Raman and near‐infrared absorption and reflectance spectroscopies
Authors: Lewis E. Neil , Kalasinsky V. F. , Levin Ira W.
Published: May 2005

A fiber‐optic sample cell designed for use in the near‐infrared region is described. For Fourier transform (FT) Raman spectroscopy, Nd:YAG laser radiation is transmitted to the sample through one fiber bundle, while a second fiber bundle collects and transfers the scattered light to the source compartment of an infrared interferometer equipped with a CaF2 beam splitter and an InGaAs detector. Because the two fiber bundles are mounted in the aluminum body of the cell, virtually no optical alignment is required. In addition to its utility in FT‐Raman spectroscopy, the cell may be used for obtaining near‐infrared absorption spectra of liquids and reflectance spectra of solids without changing its configuration. Examples of the many uses of the cell are provided, and modifications which would potentially improve its efficiency and expand its capabilities are discussed.
Raman spectroscopy at the University of São Paulo: Past, present and perspectives
Authors: Santos P. S.
Published: May 2005

We (J. R. Durig and T. S. Little, Department of Chemistry, University of South Carolina, Columbia, SC, USA) recently had an opportunity to visit the Molecular Spectroscopy Laboratory housed in the Institute of Chemistry at the University of São Paulo. This laboratory, directed and maintained by Professor O. Sala, is steeped in the history of Raman spectroscopy. The presence of the original Raman spectrograph, hand tooled by Professor Hans Stammreich in the 1940s, with the helium lamps still intact and located near the most modern of Raman equipment, created an unforgettable air of nostalgia. We kindly requested one of Professor Sala's close co‐workers (P. S. Santos) to provide the present article on the historical perspectives and significance of Raman spectroscopy at the University of São Paulo. We are pleased to present this overview to the readership of the Journal of Raman Spectroscopy.
Polarized Raman spectra of KIO4 and RbIO4 and high‐pressure Raman studies on KIO4
Authors: Al Dhahir T. A. , Bhat H. L. , Narayanan P. S. , Jayaraman A.
Published: May 2005

Polarized Raman spectra of single crystals of KIO4 and RbIO4 were obtained. The observed fundamental modes satisfy the selection rules valid for the scheelite structure. The pressure dependence of the Raman spectra of KIO4, which was investigated up to 12 Gpa, reveals a structural phase transition in the crystal near 6.5 GPa, where new peaks are observed. Above 9.8 GPa only the peaks belonging to the high‐pressure phase exist.
Fourier transform Raman spectroscopy of superconducting YBa2Cu3O7‐δ films on strontium titanate and magnesium oxide substrates
Authors: Bist H. D. , Datta T. , Little T. S. , Thigpen J. C. , Durig J. R. , Broussard P. R. , Berkley D. D.
Published: May 2005

Thin sputtered films of the high‐Tc material YBa2Cu3O7‐Δ were investigated using 180° back‐scattering geometry with Fourier transform (FT) Raman spectroscopy. It is established that the main bands in the spectra of a YBa2Cu3O7‐Δ film on strontium titanate substrate exhibit similarity with those obtained for oriented untwinned crystallites of the superconductor having their c‐axis perpendicular to the surface of the substrate. No degradation or excessive heating of the film was observed with 1.064 μm excitation for low laser powers. The film on a magnesium oxide substrate gives unique evidence of the isolated strong, featureless, almost flat continuum, producing a broad maximum near the region of the antiphase axial bending O(2)Cu(2)O(3) motions of planar oxygens at very low excitation energy. This appears to be the first application of FT‐Raman spectroscopy using near‐infrared excitation (1.064 μm) to the field of high‐temperature superconducting films and their detailed characterization.
Raman spectroscopic determination of the dissociation constants of an acetonitrile–zinc complex in aqueous solution and the enthalpy and entropy of complex dissociation
Authors: Edwards H. G. M. , Hoskins A. R. , Johnson A. F. , Lewis I. R.
Published: May 2005

The dissociation constants for an acetonitrile‐zinc complex, (CH3CN)Zn2+, were measured in aqueous solutions containing zinc salts (40‐80%, w/w) and acetonitrile by Raman spectroscopy. Quantitative measurements of the intensity of the free and complexed ν(CN) Raman bands at 2264 and 2320 cm−1, respectively, were used to determine the average enthalpy and entropy of the complex dissociation to free acetonitrile in the temperature range 293‐343 K for a 70% (w/w) solution of zinc chloride (0.052 mol) in an aqueous solution containing acetonitrile (0.024 mol); δH° and δS° values of 8.4 ± 0.5 kJ mol−1, respectively, were determined.
Conformational properties of carbonylsulphenyl compounds: Vibrational study of bis(chlorocarbonyl) disulphide, ClC(O)SSC(O)Cl
Authors: Ulic S. E. , Aymonino P. J. , Védova C. O. Della
Published: May 2005

IR data for vapour, liquid and matrix‐isolated bis(chlorocarbonyl) disulphide and Raman data for the liquid were obtained. The observed features agree with the existence of one conformer with C2 symmetry in both the liquid and vapour phases. The 13C NMR spectrum was measured and the results were compared with those for related molecules. Some stretching force constants were derived for this conformer from semi‐empirical calculations.
Raman spectra of the permanganate ion in the solid state with excitation in the near infrared
Authors: Engert C. , Kiefer W.
Published: May 2005

By means of a conventional Raman spectrometer that had been carefully designed for near‐infrared Raman excitation, it was possible to record highly resolved Raman spectra of solid polycrystalline potassium and barium permanganate. The spectra of these deeply coloured materials are of high quality and comparable to those reported hitherto, obtained using Fourier transform Raman techniques and near‐infrared excitation. Full site symmetry splitting and partial factor group splitting of the bands of the permanganate ion could be observed.
Surface‐enhanced resonance Raman scattering study on the hemicyanine dye 4‐ [2‐(4‐dimethylaminophenyl)ethenyl]‐1‐methylpyridinium iodide adsorbed on a silver electrode surface
Authors: Shibasaki Koichi , Itoh Koichi
Published: May 2005

Surface‐enhanced resonance Raman scattering (SERRS) spectra were measured at O V (vs Ag/AgCl) for a hemicyanine dye and its protonated form (HC and HCH+) adsorbed on a silver electrode surface. The surface spectrum of HC shows a characteristic feature due to a trans conformation, a band mainly due to a stretching frequency (νcc) at 1580 cm−1, which is appreciably lower than the corresponding frequency for HC in water (1592 cm−1); this result indicates that, on adsorption on the electrode surface, the resonance balance of HC between the quinoid and benzenoid forms shifts to the former. An adsorbate on a silver electrode surface from HCH+ solution at pH 1.0 takes either a protonated form, HCH+, or a deprotonated form, HC, depending on the anodization conditions of granular structures assumes the deprotonated form, whereas the adsorbate on a surface containing smooth parts retains the protonated form; hence the surface morphology is related to the chemical properties of the silver electrode surfaces. It was also found that the adsorbate in the protonated state gives a prominent SERRS band at 885 cm−1 assignable to an out‐of plane bending vibration of the central olefinic group, indicating that the adsorbate assumes a flat orientation on the silver electrode surface.
Molecular recognition using surface‐enhanced Raman scattering from citrate‐reduced silver colloids in non‐aqueous solvents
Authors: Clarkson J. , Campbell C. , Rospendowski B. N. , Smith W. E.
Published: May 2005

Surface‐enhanced Raman scattering (SERS) from citrate‐coated colloidal particles suspended in organic solvents is used to study surface reactions in an organic phase. Stable colloids which gave good SERS were produced from ethanol and acetonitrile. SERS was easily discriminated from the bulk solvent Raman scattering. Compounds which are sparingly soluble in water including 2,2′‐bipyridine and benzene‐1,2,4,5‐tetracarboxylic acid dianhydride produced good SERS in ethanol. In the latter case, no SERS was observed from an aqueous colloid. Therefore, some form of solvent‐dependent molecular recognition may operate. The formation of a bipyridine complex with copper(II) at the surface in a solvent system in which the ligand and complex are both soluble was observed. The solvent altered surface reactions. In the ethanol colloid, in contrast to the result in aqueous colloid, pyridine does not replace citrate readily. This work demonstrates the potential for the expansion of the use of colloidal SERS into the field of surface reactions in contact with an organic phase and is related to metal liquid‐like films.
Vibrational modes of CO adsorbed on disordered copper films
Authors: Akemann W. , Otto A.
Published: May 2005

The Raman spectrum of CO adsorbed on copper films featuring atomic‐scale roughness reveals four vibrational modes: a CO stretching mode at 2102 cm−1, a restricted rotation at 282 cm−1 and restricted translations normal and parallel to the local surface at 355 and 24 cm−1. The spectrum originates from a minority of CO molecules adsorbed at surface defect sites via a single coordination bond. The bond strength is increased compared with adsorption at facet sites, presumably owing to increased σ‐donation promoted by a local depletion of conduction electron density. A splitting of the translational mode into two separate frequencies, expected for adsorption sites with rotational symmetry less than C3v, is not observed. The intensities and line shapes of the SERS bands are sensitive to a thermally induced rearrangement of the molecules within the adsorbate layer. Spectra from annealed substrate films indicate dominant excitation of the rotational mode on surfaces with a lesser degree of atomic‐scale roughness. This is explained by the relevance of Herzberg‐Teller contributions to the inelastic scattering of photoexcited electrons by the surface molecules.
Surface‐enhanced Raman spectroscopy of silver etched by CrO3H2SO4: Study of adsorbed sulphate
Authors: Pagannone M. , Quagliano L. G. , Mattioli L. , Mattei G.
Published: May 2005

The surface‐enhanced Raman (SER) spectra of sulphate adsorbed on silver were obtained by treating it with a sulphochromic mixture, CrO3H2SO4. When nitrate or pyridine are added to the etching solution, there is evidence that both species can co‐adsorb with sulphate. The analysis of SER bands obtained under different conditions indicates that in some cases sulphate is perhaps physically adsorbed on the surface, preserving its free ion Td symmetry, whereas in others it is chemisorbed, presumably in the form of a bidentate complex having C2ν symmetry. The antisymmetric stretching vibrational mode ν3 of sulphate is very sensitive to the presence of species co‐adsorbed on the surface.
Raman and infrared spectra, conformational stability and ab initio calculations for chlorocarbonyl isocyanate
Authors: Sullivan J. F. , Nandy S. K. , Lee Min Joo , Durig J. R.
Published: May 2005

The Raman (2500—10 cm−1) and infrared (2600—50 cm−1) spectra of chlorocarbonyl isocyanate, CIC(O)NCO, were recorded for the gas and solid. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. The observed bands were assigned in terms of the more stable trans conformer (isocyanate grouptrans to the carbonyl bond) and less stable cis conformer. A conformer pair observed at 788 and 636 cm−1 in the Raman spectrum of the gas (775 and 634 cm−1 for the liquid) and assigned to the cis and trans COCI rock, respectively, was used to determine experimentally a ΔH value of 254 ± 48 cm−1 (726 ± 137 cal mol−1) and 230 ± 28 cm−1 (658 ± 80 cal mol−1) for the gas and liquid, respectively. In the far‐infrared spectrum of the gas, a series of three Q‐branches beginning at 83 cm−1 was observed and assigned to the fundamental torsional transition and two excited states transitions for the trans conformer. Using these three transitions and the experimentally determined ΔH value, a potential function was obtained for the interconversion of the two conformers with the following coefficients (in cm−1): V1 = −330 ± 50, V2 = 1025 ± 70, and V3 = 67 ± 40 and a trans to cis barrier of 1230 ± 150 cm−1 (3.52 ± 0.43 kcal mol−1) and a torsional frequency for the cis conformer of 69 ± 2 cm−1. The barrier to internal rotation and fundamental vibrational frequencies which were determined experimentally were compared with those obtained from ab initio Hartree—Fock gradient calculations utilizing the 6‐31G* basis set. These results are compared with some previous results on this molecule.
Vibrational spectra of NaBF4
Authors: Rajakumar V. , Krishnamurthy N. , Ramakrishnan V. , Kumar J.
Published: May 2005

Raman spectra of an NaBF4 crystal were recorded and analysed. All the group theoretically expected bands were observed and assigned unambiguously. The rotational modes could be correlated with the principal moments of inertia of the BF4 − ion.
Resonant Raman excitation profile of the 220 cm−1 mode in trans‐azobenzene
Authors: Biancalana A. , Campani E. , Gorini G. , Masetti G. , Quaglia M.
Published: May 2005

The Raman excitation profile for the 220 cm−1 mode of trans‐azobenzene in cyclohexane solution was measured in resonance with the π‐π* transition peaked around 320 nm. A strong modulation of the band intensity across the first vibrational feature of the poorly resolved absorption spectrum was detected. The collected data were analysed by means of the time‐correlator theory and of a Franck‐Condon model to derive some molecular parameters of the excited electron state.
Surface‐enhanced Raman spectra of pyrazinecarboxamide and pyrazinecarbonitrile on silver sols
Authors: Arenas J. F. , Castro J. L. , Otero J. C. , Marcos J. I.
Published: May 2005

Adsorption of pyrazinecarbonitrile and pyrazinecarboxamide on the metal surface in silver sols was investigated by the surface‐enhanced Raman Scattering (SERS) technique. Both molecules give similar spectra because the nitrile is converted into the amide by surface reaction. Pyrazinecarboxamide was found to adsorb via the substituent group with edge‐on orientation.
High‐resolution photoacoustic Raman spectroscopy of gases
Authors: Rotger M. , Lavorel B. , Chaux R.
Published: May 2005

A high‐resolution photoacoustic Raman spectroscopy experiment is described. The resolution achieved by using two single‐mode pulsed lasers is about 0.0054 cm−1 (full width at half maximum intensity). The experiment was tested first on the v1/2v2 bands of CO2 and gave an increase of at least about one order of magnitude in the signal‐to‐noise ratio with respect to stimulated Raman spectroscopy at low pressure (ca. 10 Torr ≈ 1.3 kPa). The sensitivity is also demonstrated by the study of the weak hot band v1 + v2 — v2 of CO2. In both cases, the experimental line shape is well reproduced by taking into account Doppler and collisional effects. A comparison with CARS spectra was also made.
Resonance Raman spectroscopy of non‐planar nickel porphyrins
Authors: Shelnutt J. A. , Majumder S. A. , Sparks L. D. , Hobbs J. D. , Medforth C. J. , Senge M. O. , Smith K. M. , Miura M. , Luo L. , Quirke J. M. E.
Published: May 2005

Non‐planar conformational distortions have recently been implicated in the biological activity of porphyrins and related tetrapyrroles in proteins, and several studies have used highly substituted porphyrins to model these nonplanar conformational distortions. Several aspects of non‐planarity in the highly substituted metalloporphyrins are discussed, focusing on resonance Raman spectroscopy as a technique for investigating these structural issues. First, different non‐planar distortions cause characteristic changes in the Raman spectrum. Specifically, the decreases in frequency of several Raman lines when compared with planar porphyrin analogs are shown to be similar for several classes of non‐planar highly substituted porphyrins. Second, the effect of the central metal ion [ M = Ni(II), Co(II), Cu(II), Zn(II), Co(III), Fe(III)] on the conformation of the sterically constrained non‐planar porphyrin octaethyltetraphenylporphyrin is considered. Responding to the conformational adjustments resulting from different metal size, the frequency of the structure‐sensitive Raman line v2 correlates with several structural parameters obtained from either mechanics calculations or crystallographic studies. The parameters include CβCβ bond length, core size and CαNCα angle. Finally, an effect of electron‐withdrawing substituents on the Raman frequencies is evident for the different classes of highly substituted porphyrins.
Mode‐specific relaxation dynamics of photoexcited fe(II) protoporphyrin IX in hemoglobin
Authors: Alden R. G. , Schneebeck M. C. , Ondrias M. R. , Courtney S. H. , Friedman J. M.
Published: May 2005

The behavior of the resonance Raman spectra of deoxyhemoglobin in the presence of strong resonant fields was studied by using ca. 30 ps laser pulses. The line width of the strongest Raman‐active mode in the Soret absorption band region, v4, broadens as a function of laser fluence, and its anti‐Stokes/Stokes intensity ratio is power dependent. Previous studies have suggested that equipartition of excess vibrational energy occurs on very fast time scales in the heme macrocycle subsequent to absorption of a photon. The mode‐specific vibrational dynamics of v4, however, indicate that the vibrational relaxation of the chromophore cannot be treated within the context of an equipartition of energy, but rather should be evaluated in terms of the relaxation phenomena of the specific vibrational mode. These data are evaluated in terms of relaxation mechanisms of the vibrational mode with reference to power‐broadening processes and transient vibrational population redistribution.
Mid‐ and low‐frequency Raman spectra of stable and metastable crystalline states of the 4‐n‐alkyl‐4′‐cyanobiphenyl (n = 9, 11, 12) liquid crystals
Authors: Perrot Michel , De Zen Jean‐Marc , Rothschild Walter G.
Published: May 2005

Metastable crystalline states of each of the title compounds were reproducibly generated by rapid low‐temperature quenching of the corresponding liquids, as judged by the phonon‐like appearance of their low‐frequency Raman spectra (5–200 cm−1) and by a splitting of the mid‐Raman (ca. 2220 cm−1) CN stretch. Their observed aspects of peak frequencies, peak multiplicities and band widths differ markedly from those of the corresponding spectra of the stable crystals. We propose that the solid metastable configurations consist of packings or stacks of immobilized smectic‐like structures with significant long‐range positional order within each, but with disordered director orientations between them.
Surfactant‐aided surface‐enhanced Raman scattering of Zn(II), Co(II), Ni(II), Cu(II) and free‐base tetrakis(4‐sulphonatophenyl)porphyrins
Authors: Song Ok‐Keun , Shin Eun‐Joo , Lee Minyung , Kim Dongho , Han Joo‐Tak , Jee Jong‐Gi , Yoon Minjoong
Published: May 2005

Although surface‐enhanced Raman scattering (SERS) has been recognized as a powerful tool for investigating the vibrational structure of molecules, the requirement that the molecules under study should have appropriate functional groups to interact with the metal surface has been a major problem in applying the SERS effect to many chemical or biological systems. It is shown that the introduction of a surfactant such as cetyltrimethylammonium bromide in a silver sol results in a strong Raman signal enhancement of negatively charged water‐soluble metallotetrakis(4‐sulphonatophenyl)porphyrins. Without introducing CTAB into a silver sol, these porphyrin molecules did not show any colour change and consequently no SERS effect was observed. Such a surfactant‐aided SERS effect will provide the possibility of applying SERS to new molecular systems.
CARS difference spectroscopy. I—theory for binary mixtures
Authors: Weippert A. , Kiefer W.
Published: May 2005

The theory for CARS difference spectroscopy is developed. This is an extension of linear Raman difference spectroscopy to non‐linear methods. This technique can be applied to the study of frequency shifts and band width changes in the CARS spectra of liquid mixtures or solutions when fluorescence does not allow linear Raman difference spectroscopy to be used. However, because of their coherent properties CARS spectra show complex line shapes due to interference effects between adjacent lines, which prohibits the simple subtraction of CARS spectra from one another. To make use of this technique, the spectra must be simulated with the inclusion of interference terms. The necessary theoretical treatment is outlined and some numerical model calculations for the v2(A1) Raman modes in chloroform‐deuterochloroform mixtures of different concentrations are given. Special emphasis is put on illustrating the influence of the interference effects in the CARS spectra of these mixtures.
Resonance Raman investigation of trans‐azobenzene in the lowest energy 1Au excited state
Authors: Biancalana A. , Campani E. , Di Domenico G. , Gorini G. , Masetti G.
Published: May 2005

The excitation profiles of several Raman bands of trans‐azobenzene solution in carbon tetrachloride were measured in resonance with the first allowed electronic transition peaked around 320 nm. The experimental results were analysed by means of a multi‐mode Franck–Condon model to obtain some excited state molecular parameters; such parameters were found to reproduce well the red side of the absorption band whereas some inconsistencies between experiment and calculation persist on the UV side. This has been tentatively explained as due to the contribution of a higher energy electronic state whose absorption band is peaked around 287 nm and which may slightly affect the parameters obtained.
Vibrational spectra of fluvalinate
Authors: Narayanan V. Anantha , Begun George M. , Stump Nathan A. , Stokes David L. , Vo‐Dinh Tuan
Published: May 2005

The normal Raman spectrum (NRS), Fourier transform infrared spectrum (FTIRS) and surface‐enhanced Raman spectrum (SERS) of the important insecticide and acaricide fluvalinate (C26H22ClF3N2O3) were recorded for the first time. The spectral data are discussed in terms of characteristic chemical group frequencies and bonds. The fingerprint regions of fluvalinate vibrations that are distinct in FTIRS are identified and presented with the different fingerprint frequencies that are only characteristic to NRS. The enhancement of the benzene ring‐breathing vibration of fluvalinate in SERS is a useful mode for trace analysis for residues of this pesticide at the subnanogram level. The vibrational spectra and polarization characteristics of NRS frequencies are useful as reference spectra for this pesticide in the qualitative analysis of its residues.
Anomalous frquency non‐coincidence effect in strongly interacting liquids, with special reference to molten salts
Authors: Kirillov Sviatoslav A.
Published: May 2005

The anomalous frequency non‐coincidence effect in strongly interacting liquids (ωiso < ωIR) was interpreted in terms of non‐resonant splitting caused by short‐range interparticle repulsion. The shift of the in‐phase component of the split lines was found to depend mainly on dsi/dQj, the derivative of the vibrational displacement of the ith atom with respect to the normal coordinat of jth vibration. For molten potassium thiocyanate, the numerical estimations agree well with the experimental data.
Spectroscopic studies of the thermochromism of N‐(2‐hydroxy‐4‐methoxybenzylidene)‐4‐nitroaniline
Authors: Takase Akira , Sakagami Sakumitsu , Nonaka Kazuhiro , Koga Toshiaki
Published: May 2005

Thermochromism of N‐(2‐hydroxy‐4‐methoxybenzylidene)‐4‐nitroaniline (HMBNA) was studied by Raman scattering and infrared absorption. HMBNA is yellow when freshly prepared and deepens to orange–red on heating above the melting point. On cooling at room temperature, the orange–red colour is retained for a few months. The change in colour is explained by the change in the molecular structure as indicated by the vibrational spectra. The spectra show that in the thermochromic coloured state the central group of HMBNA takes the cis‐keto amine form.
Micro‐Raman spectroscopy of sol–gel‐derived Pb(ZrxTi1 − x)O3 thin films
Authors: Agrawal D. C. , Majumder S. B. , Mohapatra Y. N. , Sathaiah S. , Bist H. D. , Katiyar R. S. , Ching‐Prado E. , Reynes A.
Published: May 2005

Thin films of ferroelectric PbZrxTi1 − xO3 were prepared by the sol–gel technique on sapphire and fused‐quartz substrates with thicknesses ranging from 0.6 to 1.2 μm. Powders of the above substance were also prepared by hydrolysis and condensation of the same precursor sol and crystallized by holding them at 600°C for either 6 or 12 h. From a comparison of the Raman spectra it is obvious that both powders and the film on sapphire substrate belong to the perovskite structure, whereas the film on fused quartz has a phyrochlore structure. These observations agree well with x‐ray measurements of diffraction patterns. Absence of 70 cm−1 E(TO) band in the film suggests that the film is rhombohedral with x being well above 0.535.
Continuum resonance Raman scattering in iodine: Time‐dependent calculations, scattering delay times and demonstration of fundamental principles
Authors: Ganz M. , Kiefer W.
Published: May 2005

Continuum resonance Raman spectra of 127I2 were numerically simulated using time‐dependent quantum theory. The calculated spectra were compared with results obtained from traditional time‐independent calculations, based on the Kramers–Heisenberg–Dirac relationship, and experimental data obtained earlier by Strempel and Kiefer. A symmetry principle for corresponding Stokes and anti‐Stokes Raman spectra is also demonstrated and the corresponding spectra for this principle were simulated applying both time‐dependent and time‐independent theory. Further aspects such as the reflection principle and scattering delay times are discussed and compared with results obtained for 79Br2.
Preparation and vibrational spectroscopic characterization of copolymers of 2,3‐dimethylbutadiene and methyl methacrylate
Authors: Edwards H. G. M. , Johnson A. F. , Lewis I. R. , Ward N. J. , Wheelwright S.
Published: May 2005

The preparation and vibrational spectroscopic characterization of the hitherto unreported products of the copolymerization of 2,3‐dimethylbutadiene and methyl methacrylate are presented. The polymers were prepared by free radical polymerization using α,α′‐azobisisobutyronitrile as the initiator. Raman and Fourier transform infrared spectroscopic information on the 2,3‐dimethylbutadiene–methyl methacrylate copolymer is presented for a range of copolymers differing in the 2,3‐dimethylbutadiene to methyl methacrylate ratio. Quantitative information of the microstructure of the polymer and copolymer using the CC stretching vibrations is provided by Raman spectroscopy. Evidence is presented for the splitting of the CO stretching vibration, ascribed to aggregated syndiotactic and unaggregated syndio‐ and isotactic poly(methyl methacrylate) at 1734 and 1724 cm−1, respectively.
Conformational stability, barriers to internal rotation, vibrational assignments and Ab Initio calculations of 3‐methylbut‐1‐ene
Authors: Durig J. R. , Tang Qun , Little T. S.
Published: May 2005

The Raman spectra (3200–10 cm−1) of gaseous, liquid and solid and infrared spectra (3200–40 cm−1) of gaseous and solid 3‐methylbut‐1‐ene, H2CCHCH(CH3)2, were recorded. From the vibrational spectra of gaseous 3‐methylbut‐1‐ene, below 200 cm−1, the asymmetric torsional mode of the more stable trans and higher energy gauche conformers were assigned. From studies of the Raman spectrum of the gas with variable temperatures the trans conformer has been determined to be more stable than the gauche form by 155 ± 31 cm−1 [443 ± 89 cal mol−1 (1 cal = 4.184 J)]. Similar studies for the liquid indicate that the two conformers are nearly equivalent in energy and for the annealed solid only the gauche conformer persists. Optimized structural parameters, obtained from ab initio calculations with the MP2/6–31G basis set, were used to obtain the kinetic energy terms with structural relaxation for the asymmetric internal rotation. The coefficients of the potential function governing the conformational interchange are V1 = 198 ± 15, V2 = 68 ± 6, V3 = 748 ± 1 and V4 = ‐55 ± 2 cm−1, and this potential has trans to gauche, gauche to gauche and gauche to trans barriers of 816, 787 and 657 cm−1, respectively. Barriers to internal rotation of the methyl rotors of 1169 cm−1 for the trans conformer and 1290 ± 30 and 1525 ± 50 cm−1 for the gauche conformer were determined from the low‐frequency Raman and far‐infrared spectra of the gas. Vibrational assignments are provided which are based on infrared band contours. Raman depolarization values, group frequencies and normal coordinate calculations. The conformational stabilities, barriers to internal rotation and fundamental vibrational frequencies which were determined from experimental data are compared with those obtained from ab initio calculations.
Raman, infrared and NMR spectra, conformational stability and ab initio calculations of trimethoxyborane
Authors: Stampf E. J. , Kim Young H. , Durig J. R.
Published: May 2005

The Raman spectra (3500–20 cm−1) of gaseous, liquid and solid and the infrared spectra (4000–50 cm−1) of gaseous and solid trimethoxyborane, B(OCH)3, were recorded. Qualitative depolarization values were obtained from the Raman spectrum of the liquid. All normal modes, except the torsions, were assigned based on infrared band contours, depolarization values, group frequencies and normal coordinate calculations. From a comparison of the spectra in the fluid states with that from the solid, it is concluded that the molecule exists predominantly in a single conformation in all physical states. Frequencies and potential energy distributions for the normal modes were calculated with the force constants obtained from ab initio calculations with the 3–21G basis set. A comparison of these calculated frequencies with the observed spectra is consistent with the predominant form having a ‘planar’ heavy atom skeleton with C3h symmetry. In was not possible to determine an experimental barrier to rotation about the BO bond. No change was observed in the 13C NMR spectrum over the temperature range of 22 to −90°C. Structural parameters, conformational stability and barriers to internal rotation were obtained from ab initio Hartree–Fock gradient calculations employing both the 3–21G and 6–31G* basis sets. The results are compared with the corresponding data for some similar organoboranes.
SERS investigation of the co‐adsorption of nicotinic acid and 3‐acetylpyridine on silver electrodes
Authors: Barthelmes J. , Pofahl G. , Panagiotakis M. , Plieth W.
Published: May 2005

The pH‐dependent solution Raman spectra of nicotinic acid and 3‐acetylpyridine are reported in the wavenumber range 500–1750 cm−1. The changes with pH in the spectra of both molecules were correlated with the structure of the predominant solution species. Band assignments were carried out by referring to the spectra of the pure compounds and of related molecules. The surface‐enhanced Raman spectra of nicotinic acid and 3‐acetylpyridine co‐adsorbed on polycrystalline silver electrodes were measured as a function of applied potential. The surface‐active species were identified according to the solution and surface Raman shifts of the individual components. A surface configuration involving the interaction of nicotinic acid and 3‐acetylpyridine is proposed to explain the observed spectra.
Raman frequency amplification in an erbium‐doped optical waveguide
Authors: Pavlov L. I. , Ivanov L. M.
Published: May 2005

Optical amplification in an erbium‐doped fibre, pumped by an argon ion laser, was investigated. Spontaneous Raman frequency generation arising from an InGaAsP Fabry–Perot‐type picosecond laser signal directed into the optical waveguide and also high amplification of the Raman components in a strongly doped fibre were produced. These have not been observed previously. A great increase in the intensity of the fundamental soliton pulse when propagation in optical fibres with length of tens of centimetres was also observed.
Vibrational study of nicotinic acid complexes with different central ions
Authors: Lewandowski Włodzimierz , Barańska Halina , Mościbroda Piotr
Published: May 2005

Assignments are proposed for the IR and Raman spectra of potassium, zinc and mercury(II) nicotinates and for the UV‐visible spectra of the f → f transition for erbium nicotinate. The influence of K, Zn, Hg(II), Nd(III), Dy(III) and Er(III) on the aromatic system of nicotinic acid was studied. There are essential differences in the number, wavenumber and intensity of aromatic system bands in the ranges of the ring modes, (1610–1400 cm−1), γ(CH) (970–700 cm−1) and Φ(CC) (700–650 cm−1), depending on the central ion. Potassium and mercury(II) perturb but lanthanides stabilize the aromatic system of nicotinic acid. The wavenumbers and intensities of some vibrational bands of the aromatic system depend systematically on the ionic potentials of the metals.
Fourier transform Raman spectroscopy of some energetic materials and propellant formulations
Authors: McNesby K. L. , Wolfe J. E. , Morris J. B. , Pesce‐Rodriguez R. A.
Published: May 2005

Fourier transform Raman (FTR) spectroscopy employing near‐IR laser radiation at 1.06 μm as the scattering source was used to obtain Raman spectra of some neat energetic materials and several propellant formulations containing those energetic materials. It is shown that only crystalline components of propellant formulations are easily detected by FTR spectroscopy. Also, FTR spectroscopy is shown to be a useful tool in determining the principle ingredient(s) in many non‐colored propellant formulations.
Raman spectroscopy of oxygenated amorphous CdTe films
Authors: Morell G. , Reynés‐Figueroa A. , Katiyar R. S. , Farías Mario H. , Espinoza‐Beltran F. J. , Zelaya‐Angel O. , Sánchez‐Sinencio F.
Published: May 2005

Oxygenated CdTe films prepared by r.f. sputtering have been shown to have band gap energies between 1.48 and 3.35 eV, depending on the amount of oxygen incorporated in the CdTe matrix. Samples with oxygen concentrations above 7 at.% are amorphous, whereas those with oxygen concentrations below 7 at.% are polycrystalline, as determined by x‐ray and Raman measurements. The Raman spectra of the polycrystalline samples show that there is ca. 4 at.% Te in the form of inclusions under high pressure, which is relatively easy to detect owing to the enhanced Raman cross‐section of Te. The Raman spectra of the amorphous samples is dominated by a single broad band at 159 cm −1. The fact that tellurates in general show a similar band, in spite of their different vibrational density of states, indicates that it corresponds to TeTe bonds in the amorphous matrix.
Infrared and Raman selection rules in diperiodic three‐dimensional layers
Authors: Burneau A.
Published: May 2005

Diperiodic three‐dimensional layers are distributed among 31 orientation classes and 80 plane groups of which 43 are symmorphic. The site symmetries of these diperiodic plane groups are tabulated. Examples of applications illustrate the determination of the first‐order selection rules for the long‐wavelength normal modes of a layer. The symmetry species of these principal modes are obtained, as in triperiodic crystals, through correlations between the reduced representation of the factor group of the layer diperiodic group and the representations of nuclear site groups, on the basis of atomic motions. Emphasis is placed on the splitting of the layer modes in a layered crystal. A procedure is described to relate a typical, quasi‐isolated layer to the real sample through a real layer in the sample, whose diperiodic group is a subgroup of both space groups corresponding to the preceding structures. The method is similar to the molecular site group analysis and provides directly, for a specific type of layer motion, the correlations between equivalent layers. The quasi‐isolated layer approximation is used to study the principal vibrations of graphite intercalation compounds and of anisotropic crystal polytypes with more than one layer per unit cell.
Raman scattering in ferroelectric (CH3NH3)3Bi2Br9 single crystals
Authors: Miniewicz A. , Jakubas R. , Ecolivet C. , Girard A.
Published: May 2005

The Raman spectra of ferroelectric (CH3NH3)3Bi2Br9 single crystals were studied at temperatures from 80 to 300 K and in the wavenumber range 0–300 cm−1. A tentative assignment of the observed bands is proposed. The phase transitions reported at 188, 140 and 101.5 K influence the Raman spectra and the observed changes are discussed in terms of the possible mechanisms involved. The lowest phase transition at 101.5 K is directly connected with instability of the inorganic sublattice.
Molecular relaxation in dimethyldichlorosilane from Raman band shape studies
Authors: Iliescu T. , Bratu I. , Grecu R. , Veres T. , Maniu D.
Published: May 2005

Rotational and vibrational relaxation of pure liquid dimethyldichlorosilane (DMDCS) at temperatures of 279, 293, 308 and 323 K and in carbon tetrachloride, dioxane, chloroform and cyclohexane solutions at 293 K were studied by Raman band shape analysis. The activation energy for molecular reorientation of DMDCS molecules was determined. The experimental vibrational correlation functions were compared with the Kubo‐Rothschild and Oxtoby relationships.
High‐resolution stimulated Raman spectrum of ethane (12C2H6) in the region of the CH symmetric stretching
Authors: Abad L. , Bermejo D. , Cancio P. , Domingo C. , Herrero V. J. , Santos J. , Tanarro I. , Montero S.
Published: May 2005

The high‐resolution (ca. 0.008 cm−1) stimulated Raman spectrum of the strongly perturbed CH symmetric stretching region of 12C2H6 at room temperature and at a rotational temperature of ca. 30 K, achieved in a free supersonic jet expansion chamber, is reported. The spectrum is tentatively analysed and assigned in terms of a simplified vibration‐torsion–rotation Hamiltonian. Besides the already known strong Fermi resonance, several Coriolis torsional interactions are identified as the major perturbations in this spectral region.
Vibrational dephasing times of bis(dimethylamino)heptamethine iodide determined by CARS using incoherent light
Authors: Lau A. , Kummrow A. , Pfeiffer M. , Woggon S.
Published: May 2005

Interferometric coherent anti‐Stokes Raman scattering (ICARS) using incoherent laser light was used for time‐resolved measurements of vibrational parameters of solutions of bis(dimethylamino)heptamethine iodide in the ground and the S1, state. The vibrations at 1124, 1195, 1285 and 1304 cm−1 have dephasing times in the range 0.3–1.1 ps. The shortest dephasing time is observed for the normal mode at 1195 cm−1 with a large amplitude for the N atoms. The coherence peak in the ICARS signal around zero delay is broadened due to coupling to the electronic transition. The same peak width of 80 fs is found using degenerate four‐wave mixing.
Fourier transform Raman study of acid—base interactions via guanosine N‐7 in solid complexes and in strongly acidic solutions
Authors: Bertoluzza A. , Fini G. , Tosi M. R. , Tugnoli V.
Published: May 2005

Among the nucleosides, guanosine shows an anomalous behaviour which has been related to various factors (conformation, H‐bonding, self‐association, etc.), which characterize this nucleoside in relation to the others. It also easily forms a gel, the structure of which is well known. This work concerns the Raman vibrational spectroscopic characterization of the reactivity of guanosine N‐7, which is one of the main factors responsible for the anomalous behaviour of guanosine. For this purpose, some of its acid–base solid complexes and strongly acidic aqueous solutions were studied. In particular, this study considers the two Raman bands at about 1480 and 1540 cm−1, attributable to vibration modes with prevailing imidazolic character, N‐7 of free guanosine or bonded guanosine, respectively. In addition, the acid–base interaction via the H‐bond of N‐7 and the proton transfer in relation to the ΔpKa. of the interacting group were studied.
Structure, intermolecular interactions and molecular mobility in aqueous solutions of decylammonium chloride
Authors: Ferrari G. , Zerbi G.
Published: May 2005

The temperature‐dependent vibrational infrared and Raman spectra of 20% solutions of decylammonium chloride in H2O (D2O) were studied. According to previous work, phases SI and SII were identified in the low‐temperature range. Molecular and supermolecular structures were derived. The upper shift (Δν = 12 cm−1) of the Raman‐active antisymmetric stretching CH2 mode (d−) and its narrowness are peculiar and specific signals of a specific structure. It is proposed that the phase transition SI → SII is originated by the onset of a conformational flexibility generally described as twistons or conformational solitons. No evidence was found that the alkyl residues have librational freedom about their axes.
Pre‐resonance Raman effect of some croconates in the solid state
Authors: Gonçalves Norberto Sanches , Shamir Jacob , Santos Paulo Sergio
Published: May 2005

The optical and Raman spectra of several salts of croconic acid were investigated in order to obtain a better understanding of solid‐state effects. The results indicate that for the sodium and barium salts the perturbations can be ascribed to a decrease in the local symmetry of the anion. On the other hand, for the thallium and silver salts the perturbations are much more dramatic, clearly indicating the presence of charge‐transfer effects. For the silver salt, the abnormal enhancement in the Raman spectrum is ascribed to the presence of silver microparticles in the surface of the solid.
Low‐temperature order–disorder phase transition of PLZT x: 95:5 ceramics, with La Content x = 0.5–4% by weight, determined by Raman spectroscopy
Authors: El‐Harrad I. , Carabatos‐Nédelec C. , Handerek J. , Ujma Z. , Dmytrow D.
Published: May 2005

Investigations of the Raman spectra of lead–lanthanum–zirconate‐titanates (PLZT) x:95:5 (x = 0.5, 1, 2, 3 and 4 wt.% La2O3) ceramics over a range of temperature from 10 K to room temperature are presented. With increasing temperature the intensity of the Raman spectra, corrected for the Bose population factor, is lower above the transition temperature T0 = 130 K; this intensity lowering is characteristic of disorder‐induced spectra. This temperature dependence is interpreted by means of the theory of fluctuating clusters in the low‐temperature phase and the order parameter below T0 was determined. Associated with this phase transition, it was found that some softening effects are present in the vibrational wavenumbers.
Micro‐Raman spectroscopic study of organ cultured corneae
Authors: Siew Diana C. W. , Clover Gillian M. , Cooney Ralph P. , Wiggins Phillipa M.
Published: May 2005

Raman spectroscopy of water was used to assess the metabolic state of fresh corneae and those which had been stored under long‐term organ culture conditions. Both human and porcine tissue were employed. The data showed a semi‐quantitative relationship between corneal hydration (determined using wet and dry weights of the tissue) and the integrated intensity of the water to collagen bands in the spectral region 2700—4000 cm−1. Variables included duration of storage, composition of culture medium and, for the human specimens, the age of the cornea. Raman assessment of hydration may provide a better measure of the functional state of the stored cornea that the density of live endothelial cells, which is a commonly used criterion. The spectra showed that the healthy cornea of low water content contained more weakly hydrogen‐bonded water than either bulk water or a swollen cornea. This is to be expected as groups on proteins and proteoglycans in the cornea form weak bonds with water. These weakly bonded surface groups are diluted when water is imbibed, hence resulting in the spectrum becoming more like that of bulk water in swollen tissue. Addition to the culture medium of dextran, which osmotically thins the cornea, converted its water spectrum back towards that of a healthy cornea.
Resonance Raman and infrared studies of the organic superconductor k‐(MDT‐TTF)2AuI2 in the normal state
Authors: Zambounis J. S. , Patsis A. P. , Kamitsos E. I. , Mayer C. W. , Papavassiliou G. C.
Published: May 2005

Resonance Raman and infrared spectra of the organic superconductor K‐(MDT‐TTF)2AuI2 were measured to identify the vibrational modes which exhibit strong electron—molecular vibration (EMV) coupling. Excitation wave‐length dependence of certain Raman modes was observed and is discussed in connection with the UV—visible absorption spectrum. Raman spectra measured at 77 K revealed a significant enhancement of a low‐wavenumber mode attributed to the organic part, while the symmetric AuI2− anion was found to be unaffected at low temperatures.
Raman and infrared spectra, conformational stability, vibrational assignment and ab initio calculations of methyl cyanoformate
Authors: Durig J. R. , Groner P. , Drew A. S. , Guirgis Gamil A. , van der Veken B. J.
Published: May 2005

The Raman (3100–10 cm−1) spectra of the liquid and solid and the infrared (3100—400 cm− 1) spectra of the gas and solid were recorded for three isotopic species of methyl cyanoformate, 12CH3OCOCN, 13CH3OCOCN and CH318OCOCN. Additionally, the far‐infrared (370—60 cm− 1) spectrum of the gas of the normal species was recorded. Raman depolarization ratios were obtained for the liquid phases of all three isotopic species. These data were interpreted on the basis that the only stable conformation present at ambient temperature is the s‐trans rotamer where the methyl group is trans to the cyano group. As predicted by ab initio calculations using the MP2/6—31G* basis set, the infrared intensity of the methyl torsion is very weak and, subsequently, this fundamental is not observed in the far‐infrared spectrum of the gas. Therefore, an experimental barrier to internal rotation for the methyl group could not be obtained from the vibrational data. However, the theoretical barrier to internal rotation was calculated to be 424 cm− 1 (1.21 kcal mol− 1) using the RHF/6—31G* basis set. The structure, infrared intensities, Raman activities and vibrational wavenumbers for the s‐trans conformer were also determined from ab initio calculations using the RHF/3—21G, RHF/6—31G* and MP2/6—31G* basis sets. These results are compared with those obtained experimentally and with similar quantities for some related molecules.
Infrared and Raman spectra of crystallization water in potassium N, N‐dimethyloxathioamidate monohydrate
Authors: Desseyn H. O. , Hereygers M. L. B. F. , Perlepes S. P.
Published: May 2005

Raman and infrared measurements were performed on hydrated (H2O and D2O) and anhydrous (CH3)2NCSCOOK together with their CD3‐substituted analogues. Close scrutiny of the water fundamentals indicated that the C2v symmetry of the single water molecule is lost owing to different strengths of hydrogen bonding with the carboxylate and thioamide functional groups. The number of water fundamentals and the wavenumber and intensity changes at different temperatures are, considering the very complex structure of the water spectra, unexpectedly consistent with the predictions of a single asymmetric water molecule.